java无法启动活动ComponentInfo LogCat
我不知道这些错误是什么意思，也不知道为什么应用程序无法启动：( 我在AndroidManifest中有正确的名字。我的活动 包装也是一样的
日志：
08-24 23:38:55.605 370-370/com.example.shinobi.fatburnheartratecalc W/ActivityThread﹕ Application com.example.shinobi.fatburnheartratecalc is waiting for the debugger on port 8100...
08-24 23:38:55.615 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ Sending WAIT chunk
08-24 23:38:55.775 370-375/com.example.shinobi.fatburnheartratecalc I/dalvikvm﹕ Debugger is active
08-24 23:38:55.826 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ Debugger has connected
08-24 23:38:55.826 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:56.025 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:56.224 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:56.425 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:56.635 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:56.835 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:57.035 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:57.235 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:57.435 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:57.645 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ waiting for debugger to settle...
08-24 23:38:57.845 370-370/com.example.shinobi.fatburnheartratecalc I/System.out﹕ debugger has settled (1449)
08-24 23:38:58.805 370-370/com.example.shinobi.fatburnheartratecalc D/AndroidRuntime﹕ Shutting down VM
08-24 23:38:58.815 370-370/com.example.shinobi.fatburnheartratecalc W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x40015560)
08-24 23:38:58.875 370-370/com.example.shinobi.fatburnheartratecalc E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.shinobi.fatburnheartratecalc/com.example.shinobi.fatburnheartratecalc.MyActivity}: java.lang.NullPointerException
at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
at 安卓.app.ActivityThread.access$1500(ActivityThread.java:117)
at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
at 安卓.os.Handler.dispatchMessage(Handler.java:99)
at 安卓.os.Looper.loop(Looper.java:123)
at 安卓.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.NullPointerException
at 安卓.app.Activity.findViewById(Activity.java:1647)
at com.example.shinobi.fatburnheartratecalc.MyActivity.<init>(MyActivity.java:22)
at java.lang.Class.newInstanceImpl(Native Method)
at java.lang.Class.newInstance(Class.java:1409)
at 安卓.app.Instrumentation.newActivity(Instrumentation.java:1021)
at 安卓.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)
at 安卓.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
at 安卓.app.ActivityThread.access$1500(ActivityThread.java:117)
at 安卓.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
at 安卓.os.Handler.dispatchMessage(Handler.java:99)
at 安卓.os.Looper.loop(Looper.java:123)
at 安卓.app.ActivityThread.main(ActivityThread.java:3683)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:507)
at com.安卓.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
at com.安卓.internal.os.ZygoteInit.main(ZygoteInit.java:597)
at dalvik.system.NativeStart.main(Native Method)
08-24 23:39:02.155 370-370/com.example.shinobi.fatburnheartratecalc I/Process﹕ Sending signal. PID: 370 SIG: 9
device not found
AndroidManifest。xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
package="com.example.shinobi.fatburnheartratecalc" >
<application
安卓:allowBackup="true"
安卓:icon="@drawable/ic_launcher"
安卓:label="@string/app_name"
安卓:theme="@style/AppTheme" >
<activity
安卓:name=".MyActivity"
安卓:label="@string/app_name" >
<intent-filter>
<action 安卓:name="安卓.intent.action.MAIN" />
<category 安卓:name="安卓.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
我的活动。xml
<LinearLayout xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
xmlns:tools="http://schemas.安卓.com/tools"
安卓:layout_width="fill_parent"
安卓:layout_height="fill_parent"
安卓:paddingLeft="@dimen/activity_horizontal_margin"
安卓:paddingRight="@dimen/activity_horizontal_margin"
安卓:paddingTop="@dimen/activity_vertical_margin"
安卓:paddingBottom="@dimen/activity_vertical_margin"
tools:context=".MyActivity">
<TabHost
安卓:layout_width="fill_parent"
安卓:layout_height="fill_parent"
安卓:id="@+id/tabHost"
安卓:layout_weight="1">
<LinearLayout
安卓:layout_width="fill_parent"
安卓:layout_height="fill_parent"
安卓:orientation="vertical">
<TabWidget
安卓:id="@安卓:id/tabs"
安卓:layout_width="fill_parent"
安卓:layout_height="wrap_content"></TabWidget>
<FrameLayout
安卓:id="@安卓:id/tabcontent"
安卓:layout_width="fill_parent"
安卓:layout_height="fill_parent">
<LinearLayout
安卓:id="@+id/Calc"
安卓:layout_width="fill_parent"
安卓:layout_height="fill_parent"
安卓:orientation="vertical">
<EditText
安卓:layout_width="fill_parent"
安卓:layout_height="wrap_content"
安卓:inputType="number"
安卓:ems="10"
安卓:id="@+id/inWiek"
安卓:layout_gravity="center_horizontal"
安卓:layout_marginTop="50dp"
安卓:hint="Your Age" />
<EditText
安卓:layout_width="fill_parent"
安卓:layout_height="wrap_content"
安卓:inputType="number"
安卓:ems="10"
安卓:id="@+id/inTspocz"
安卓:layout_marginTop="25dp"
安卓:hint="Your resting heart rate (Hint)" />
<Button
安卓:layout_width="100dp"
安卓:layout_height="50dp"
安卓:id="@+id/Btn"
安卓:layout_gravity="center_horizontal"
安卓:layout_marginTop="40dp"
安卓:hint="Do it" />
</LinearLayout>
<LinearLayout
安卓:id="@+id/Hints"
安卓:layout_width="fill_parent"
安卓:layout_height="fill_parent">
</LinearLayout>
</FrameLayout>
</LinearLayout>
</TabHost>
</LinearLayout>
我的活动。爪哇
package com.example.shinobi.fatburnheartratecalc;
import 安卓.support.v7.app.ActionBarActivity;
import 安卓.os.Bundle;
import 安卓.text.Editable;
import 安卓.text.TextWatcher;
import 安卓.view.Menu;
import 安卓.view.MenuItem;
import 安卓.view.View;
import 安卓.widget.Button;
import 安卓.widget.EditText;
import 安卓.widget.TabHost;
import 安卓.widget.Toast;
public class MyActivity extends ActionBarActivity {
EditText wiekEditText = (EditText) findViewById(R.id.inWiek);
EditText tspoczEditText = (EditText) findViewById(R.id.inTspocz);
int Wynik;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_my);
int Tmax, RT;
int wiek = Integer.parseInt(wiekEditText.getText().toString());
int tspocz = Integer.parseInt(tspoczEditText.getText().toString());
Tmax = 220 - wiek;
RT = Tmax - tspocz;
Wynik = 70*RT/100 + tspocz;
TabHost tabHost = (TabHost) findViewById(R.id.tabHost);
tabHost.setup();
TabHost.TabSpec tabSpec = tabHost.newTabSpec("Calc");
tabSpec.setContent(R.id.Calc);
tabSpec.setIndicator("Calc");
tabHost.addTab(tabSpec);
tabSpec = tabHost.newTabSpec("Hints");
tabSpec.setContent(R.id.Hints);
tabSpec.setIndicator("Hints");
tabHost.addTab(tabSpec);
final Button Btn = (Button) findViewById(R.id.Btn);
Btn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getApplicationContext(),"blablabla"+ Wynik,Toast.LENGTH_SHORT).show();
}
});
wiekEditText.addTextChangedListener(new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
Btn.setEnabled(!(wiekEditText.getText().toString().trim().isEmpty()));
}
@Override
public void afterTextChanged(Editable s) {
}
}); {
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.my, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == R.id.action_settings) {
return true;
}
return super.onOptionsItemSelected(item);
}
}
# 1 楼答案
你的问题是：
您正在查找布局膨胀之前的视图，因此
NullPointerException在
setContentView()之后的onCreate()中移动此项