安卓设置列表视图元素的文本导致应用程序崩溃，MeasureHeaghtToChildren上出现java nullpointer异常

Question

这是假定显示联系人信息的活动。如您所见，此活动将显示联系人的基本信息，如姓名、手机等。它还必须显示相应联系人的地址列表

public class ViewContactActivity extends Activity 
{
private TextView name;
private TextView cellphone;
private TextView displayCellphone;
private TextView workphone;
private TextView displayWorkphone;
private TextView email;
private TextView displayEmail;

private ListView listView;

private Contact contact;
private ArrayList<Address> addressList;


@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_view_contact);

    this.name = (TextView) findViewById(R.id.nameTextView);
    this.cellphone = (TextView) findViewById(R.id.cellViewTextView);
    this.displayCellphone = (TextView) findViewById(R.id.cellDisplayTextView);
    this.workphone = (TextView) findViewById(R.id.workViewTextView);
    this.displayWorkphone = (TextView) findViewById(R.id.workDisplayTextView);
    this.email = (TextView) findViewById(R.id.emailViewTextView);
    this.displayEmail = (TextView) findViewById(R.id.emailDisplayTextView);

    this.listView = (ListView) findViewById(R.id.addressListView);

    Intent i = getIntent();
    contact = (Contact) i.getSerializableExtra("Contact");

    this.name.setText(contact.getFirstName() + " " + contact.getLastName());
    this.displayCellphone.setText(contact.getCellPhone());
    this.displayWorkphone.setText(contact.getWorkPhone());
    this.displayEmail.setText(contact.getEmail());
}

protected void onResume()
{
    super.onResume();
    this.addressList = contact.getAddresses();
    populateList();
}

@Override
public boolean onCreateOptionsMenu(Menu menu) 
{
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.view_contact, menu);
    return true;
}

public boolean onOptionsItemSelected(MenuItem item) 
{
    switch (item.getItemId()) 
    {
        case 安卓.R.id.home:
            NavUtils.navigateUpFromSameTask(this);
            return true;
    }

    return onOptionsItemSelected(item);
}

private void populateList() {
    ArrayAdapter<Address> adapter = new AddressListAdapter();
    listView.setAdapter(adapter);
}

 private class AddressListAdapter extends ArrayAdapter<Address> {
        public AddressListAdapter() {
            super (ViewContactActivity.this, R.layout.address_listview_item, addressList);
        }

        @Override
        public View getView(int position, View view, ViewGroup parent) {
            if (view == null)
                view = getLayoutInflater().inflate(R.layout.address_listview_item, parent, false);

            Address address = addressList.get(position);


            TextView addressName = (TextView) findViewById(R.id.addressNameTextView);
            addressName.setText(address.getAddressName());
            TextView addressStreet = (TextView) findViewById(R.id.streetDisplayTextView);
            addressStreet.setText(address.getAddressStreet());
            TextView addressNumber = (TextView) findViewById(R.id.numberDisplayTextView);
            addressNumber.setText(address.getAddressNumber());
            TextView addressCity = (TextView) findViewById(R.id.cityDisplayTextView);
            addressCity.setText(address.getAddressCity());
            TextView addressState = (TextView) findViewById(R.id.stateDisplayTextView);
            addressState.setText(address.getAddressState());
            TextView addressZip = (TextView) findViewById(R.id.zipDisplayTextView);
            addressZip.setText(address.getAddressZip());

            return view;
        }
    }

}

这是主要的活动。当用户单击联系人时，它会启动ViewContactActivity

public class MainActivity extends Activity 
{
private ListView listView;
ShowFieldsNewContactActivity activity  = new ShowFieldsNewContactActivity();
public static ContactsManager cManager = new ContactsManager();
private Object[] Contacts;

@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    this.listView = (ListView) findViewById(R.id.contactListView);
}

protected void onResume()
{
    super.onResume();
    Contacts = cManager.getContactListObj();

    this.listView.setOnItemClickListener(new OnItemClickListener()
    {

        @Override
        public void onItemClick(AdapterView<?> arg0, View arg1, int arg2,
                long arg3) {
            Intent intent = new Intent(MainActivity.this, ViewContactActivity.class);
            intent.putExtra("Contact", (Contact) Contacts[arg2]);
            startActivity(intent);
        }

    });

    populateList();

}

@Override
public boolean onCreateOptionsMenu(Menu menu) 
{
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item)
{
    switch(item.getItemId())
    {
        case R.id.add_contact:
            Intent intent = new Intent(MainActivity.this, ShowFieldsNewContactActivity.class);
            startActivity(intent);
            //adapter.notifyDataSetChanged();

            return true;

        default:
            return super.onOptionsItemSelected(item);
    }
}

private void populateList() {
    ArrayAdapter<Object> adapter = new ContactListAdapter();
    listView.setAdapter(adapter);
}

 private class ContactListAdapter extends ArrayAdapter<Object> {
        public ContactListAdapter() {
            super (MainActivity.this, R.layout.listview_item,  Contacts);
        }

        @Override
        public View getView(int position, View view, ViewGroup parent) {
            if (view == null)
                view = getLayoutInflater().inflate(R.layout.listview_item, parent, false);

            Contact currentContact = (Contact) Contacts[position];

            TextView name = (TextView) view.findViewById(R.id.contactName);
            name.setText(currentContact.getFirstName() + " " + currentContact.getLastName());
            TextView phone = (TextView) view.findViewById(R.id.phoneNumber);
            phone.setText(currentContact.getCellPhone());
            TextView email = (TextView) view.findViewById(R.id.emailAddress);
            email.setText(currentContact.getEmail());

            return view;
        }
    }

}

接触活动

@SuppressWarnings("serial")
public class Contact implements Comparable<Contact>, Serializable
{
private String firstName;
private String lastName;
private String cellPhone;
private String workPhone;
private String email;

private ArrayList<Address> addresses;

public Contact(String firstName, String lastName, String cellPhone, String workPhone, String email)
{
    this.firstName = firstName;
    this.lastName = lastName;
    this.cellPhone = cellPhone;
    this.workPhone = workPhone;
    this.email = email;
    this.addresses = new ArrayList<Address>();

}

public String getFirstName() 
{
    return firstName;
}

public void setFirstName(String firstName) 
{
    this.firstName = firstName;
}

public String getLastName() 
{
    return lastName;
}

public void setLastName(String lastName) 
{
    this.lastName = lastName;
}

public String getCellPhone() 
{
    return cellPhone;
}

public void setCellPhone(String cellPhone) 
{
    this.cellPhone = cellPhone;
}

public String getWorkPhone() 
{
    return workPhone;
}

public void setWorkPhone(String workPhone) 
{
    this.workPhone = workPhone;
}

public String getEmail() 
{
    return email;
}

public void setEmail(String email) 
{
    this.email = email;
}

public void addAddress(Address address1)
{
    this.addresses.add(address1);
}

public ArrayList<Address> getAddresses()
{
    return this.addresses;
}

@Override
public int compareTo(Contact another) {
    // TODO Auto-generated method stub
    return 0;
}

}

添加地址活动

public class AddAdressActivity extends Activity
{
private TextView addressName;
private TextView addressStreet;
private TextView addressNumber;
private TextView addressCity;
private TextView addressState;
private TextView addressZip;

private EditText addressNameEditText;
private EditText addressStreetEditText;
private EditText addressNumberEditText;
private EditText addressCityEditText;
private EditText addressStateEditText;
private EditText addressZipEditText;

public static Contact contact;

@Override
protected void onCreate(Bundle savedInstanceState) 
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_add_adress);

    this.addressName = (TextView) findViewById(R.id.adressNameTextView);
    this.addressStreet = (TextView) findViewById(R.id.streetTextView);
    this.addressNumber = (TextView) findViewById(R.id.numberTextView);
    this.addressCity = (TextView) findViewById(R.id.cityTextView);
    this.addressState = (TextView) findViewById(R.id.stateTextView);
    this.addressZip = (TextView) findViewById(R.id.zipTextView);

    this.addressNameEditText = (EditText) findViewById(R.id.adreesNameEditText);
    this.addressStreetEditText = (EditText) findViewById(R.id.streetEditText);
    this.addressNumberEditText = (EditText) findViewById(R.id.numberEditText);
    this.addressCityEditText = (EditText) findViewById(R.id.cityEditText);
    this.addressStateEditText = (EditText) findViewById(R.id.stateEditText);
    this.addressZipEditText = (EditText) findViewById(R.id.zipEditText);

    Intent i = getIntent();
    contact = (Contact) i.getSerializableExtra("Contact");

}

@Override
public boolean onCreateOptionsMenu(Menu menu) 
{
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.add_adress, menu);
    return true;
}

public boolean onOptionsItemSelected(MenuItem item) 
{
    switch (item.getItemId()) 
    {
        case 安卓.R.id.home:
            NavUtils.navigateUpFromSameTask(this);
            return true;

        case R.id.save_contact:
            Address address = new Address(this.addressNameEditText.getText().toString(), this.addressStreetEditText.getText().toString(),
                    this.addressNumberEditText.getText().toString(), this.addressCity.getText().toString(), this.addressStateEditText
                    .getText().toString(), this.addressZipEditText.getText().toString());
            MainActivity.cManager.addContact(contact);
            contact.addAddress(address);
            finish();
            return true;

    }
    return super.onOptionsItemSelected(item);
}

}

这是查看联系人活动的XML文件

<RelativeLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
xmlns:tools="http://schemas.安卓.com/tools"
安卓:layout_width="match_parent"
安卓:layout_height="match_parent"
安卓:paddingBottom="@dimen/activity_vertical_margin"
安卓:paddingLeft="@dimen/activity_horizontal_margin"
安卓:paddingRight="@dimen/activity_horizontal_margin"
安卓:paddingTop="@dimen/activity_vertical_margin"
tools:context=".ViewContactActivity" >

<TextView
    安卓:id="@+id/nameTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignParentTop="true"
    安卓:layout_centerHorizontal="true"
    安卓:layout_marginTop="16dp"
    安卓:text="Large Text"
    安卓:textAppearance="?安卓:attr/textAppearanceLarge" />

<TextView
    安卓:id="@+id/cellViewTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignParentLeft="true"
    安卓:layout_below="@+id/nameTextView"
    安卓:layout_marginLeft="16dp"
    安卓:layout_marginTop="23dp"
    安卓:text="@string/cell_phone" />

<TextView
    安卓:id="@+id/workViewTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/cellViewTextView"
    安卓:layout_below="@+id/cellViewTextView"
    安卓:layout_marginTop="16dp"
    安卓:text="@string/work_phone" />

<TextView
    安卓:id="@+id/emailViewTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/workViewTextView"
    安卓:layout_below="@+id/workViewTextView"
    安卓:layout_marginTop="14dp"
    安卓:text="@string/email" />

<TextView
    安卓:id="@+id/workDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignBottom="@+id/workViewTextView"
    安卓:layout_alignLeft="@+id/cellDisplayTextView"
    安卓:text="TextView" />

<TextView
    安卓:id="@+id/cellDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignBaseline="@+id/cellViewTextView"
    安卓:layout_alignBottom="@+id/cellViewTextView"
    安卓:layout_alignLeft="@+id/nameTextView"
    安卓:layout_marginLeft="63dp"
    安卓:text="TextView" />

<TextView
    安卓:id="@+id/emailDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignBaseline="@+id/emailViewTextView"
    安卓:layout_alignBottom="@+id/emailViewTextView"
    安卓:layout_alignLeft="@+id/workDisplayTextView"
    安卓:text="TextView" />

<ListView
    安卓:id="@+id/addressListView"
    安卓:layout_width="match_parent"
    安卓:layout_height="wrap_content"
    安卓:layout_alignParentRight="true"
    安卓:layout_below="@+id/emailViewTextView"
    安卓:layout_marginTop="16dp" >
</ListView>

</RelativeLayout>

这是地址作为列表视图项的XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
安卓:layout_width="match_parent"
安卓:layout_height="match_parent"
安卓:orientation="vertical" >

<TextView
    安卓:id="@+id/addressNameTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignParentLeft="true"
    安卓:layout_alignParentTop="true"
    安卓:layout_marginLeft="15dp"
    安卓:layout_marginTop="16dp"
    安卓:text="Medium Text"
    安卓:textAppearance="?安卓:attr/textAppearanceMedium" />

<TextView
    安卓:id="@+id/addressStreetTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/addressNameTextView"
    安卓:layout_below="@+id/addressNameTextView"
    安卓:layout_marginTop="16dp"
    安卓:text="@string/street_text_view" />

<TextView
    安卓:id="@+id/addressNumberTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/addressStreetTextView"
    安卓:layout_below="@+id/addressStreetTextView"
    安卓:layout_marginTop="17dp"
    安卓:text="@string/addres_number_text_view" />

<TextView
    安卓:id="@+id/addressStateTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/addressCityTextView"
    安卓:layout_below="@+id/addressCityTextView"
    安卓:layout_marginTop="14dp"
    安卓:text="@string/state_text_view" />

<TextView
    安卓:id="@+id/addressZipTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/addressStateTextView"
    安卓:layout_below="@+id/addressStateTextView"
    安卓:layout_marginTop="14dp"
    安卓:text="@string/zip_code_text_view" />

<TextView
    安卓:id="@+id/addressCityTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignLeft="@+id/addressNumberTextView"
    安卓:layout_below="@+id/addressNumberTextView"
    安卓:layout_marginTop="15dp"
    安卓:text="@string/city_text_view" />

<TextView
    安卓:id="@+id/stateDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignBottom="@+id/addressStateTextView"
    安卓:layout_alignRight="@+id/cityDisplayTextView"
    安卓:text="TextView" />

<TextView
    安卓:id="@+id/zipDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_alignBottom="@+id/addressZipTextView"
    安卓:layout_alignLeft="@+id/stateDisplayTextView"
    安卓:text="TextView" />

<TextView
    安卓:id="@+id/cityDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_above="@+id/addressStateTextView"
    安卓:layout_alignLeft="@+id/numberDisplayTextView"
    安卓:text="TextView" />

<TextView
    安卓:id="@+id/streetDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_above="@+id/addressNumberTextView"
    安卓:layout_marginLeft="29dp"
    安卓:layout_toRightOf="@+id/addressNameTextView"
    安卓:text="TextView" />

<TextView
    安卓:id="@+id/numberDisplayTextView"
    安卓:layout_width="wrap_content"
    安卓:layout_height="wrap_content"
    安卓:layout_above="@+id/addressCityTextView"
    安卓:layout_alignLeft="@+id/streetDisplayTextView"
    安卓:text="TextView" />

</RelativeLayout>

最后，这就是给我的日志

04-03 02:27:03.566: E/AndroidRuntime(1930): FATAL EXCEPTION: main
04-03 02:27:03.566: E/AndroidRuntime(1930): Process: com.example.contactlist, PID: 1930
04-03 02:27:03.566: E/AndroidRuntime(1930): java.lang.NullPointerException
04-03 02:27:03.566: E/AndroidRuntime(1930):     at             edu.uprm.ece.icom4035.activities.ViewContactActivity$AddressListAdapter.getView(ViewContactA    ctivity.java:112)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at          安卓.widget.AbsListView.obtainView(AbsListView.java:2263)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at     安卓.widget.ListView.measureHeightOfChildren(ListView.java:1263)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.widget.ListView.onMeasure(ListView.java:1175)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.View.measure(View.java:16497)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.widget.RelativeLayout.measureChild(RelativeLayout.java:689)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.widget.RelativeLayout.onMeasure(RelativeLayout.java:473)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.View.measure(View.java:16497)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.View.measure(View.java:16497)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at com.安卓.internal.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:327     )
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.View.measure(View.java:16497)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.widget.FrameLayout.onMeasure(FrameLayout.java:310)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at com.安卓.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.View.measure(View.java:16497)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1916)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1295)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5670)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.Choreographer.doCallbacks(Choreographer.java:574)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.Choreographer.doFrame(Choreographer.java:544)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.os.Handler.handleCallback(Handler.java:733)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.os.Handler.dispatchMessage(Handler.java:95)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.os.Looper.loop(Looper.java:136)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at 安卓.app.ActivityThread.main(ActivityThread.java:5017)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at   java.lang.reflect.Method.invokeNative(Native Method)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at java.lang.reflect.Method.invoke(Method.java:515)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:595)
04-03 02:27:03.566: E/AndroidRuntime(1930):     at dalvik.system.NativeStart.main(Native       Method)

我试图解决这个问题，但我不太了解原木猫给我的测量高度信息

提前谢谢

Answer 1

在ViewContactActivity中。地址列表适配器。getView（）您应该使用：

TextView addressName = (TextView) view.findViewById(R.id.addressNameTextView);

而不是：

TextView addressName = (TextView) findViewById(R.id.addressNameTextView);

Answer 2

在getView中，必须使用膨胀视图来检索行项目。对于getView中的每个findViewById，将从findViewById更改为view.findViewById。比如说

TextView addressName = (TextView) findViewById(R.id.addressNameTextView);
addressName.setText(address.getAddressName());

到

TextView addressName = (TextView) view.findViewById(R.id.addressNameTextView);
addressName.setText(address.getAddressName());