java在SearchView上获取空对象引用

Question

我正在制作一个安卓应用程序，在其中我添加了一个菜单文件，在其中我添加了一个项目来执行搜索。然后在main活动中，我添加了一个searchView变量，我试图在onCreatOptionsmenu()方法中对其进行膨胀。当我尝试运行应用程序时，我收到了以下错误：“java.lang.NullPointerException:尝试在空对象引用上调用虚拟方法'void 安卓.widget.SearchView.setSearchableInfo（安卓.app.SearchableInfo）'”

这是我的主菜单的代码。xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:安卓="http://schemas.安卓.com/apk/res/安卓"
    xmlns:app="http://schemas.安卓.com/apk/res-auto">
        <item
            安卓:title="@string/search"
            安卓:orderInCategory="1"
            app:showAsAction ="ifRoom"
            安卓:id="@+id/action_search"
            />

</menu>

searchview的主要活动代码

public class MainActivity extends AppCompatActivity {
private SearchView searchView;
 @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        SearchManager searchManager = (SearchManager) getSystemService(Context.SEARCH_SERVICE);
        searchView = (SearchView) menu.findItem(R.id.action_search)
                .getActionView();
        searchView.setSearchableInfo(searchManager.getSearchableInfo(getComponentName()));
        searchView.setMaxWidth(Integer.MAX_VALUE);

        searchView.setOnQueryTextListener(new SearchView.OnQueryTextListener() {
            @Override
            public boolean onQueryTextSubmit(String query) {
                mCorona_Stats_Adapter.getFilter().filter(query);
                return false;
            }

            @Override
            public boolean onQueryTextChange(String newText) {
                mCorona_Stats_Adapter.getFilter().filter(newText);
                return false;
            }
        });
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        int menuItemThatWasSelected = item.getItemId();
        if(menuItemThatWasSelected == R.id.action_search){
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onBackPressed() {
        if (!searchView.isIconified()) {
            searchView.setIconified(true);
            return;
        }
        super.onBackPressed();
    }
}

建造。格拉德尔

apply plugin: 'com.安卓.application'

安卓 {
    compileSdkVersion 29
    buildToolsVersion "29.0.2"
    defaultConfig {
        applicationId "com.passengerearth.coronago"
        minSdkVersion 15
        targetSdkVersion 29
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "安卓x.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-安卓-optimize.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation '安卓x.appcompat:appcompat:1.0.2'
    implementation '安卓x.constraintlayout:constraintlayout:1.1.3'
    implementation 'com.google.安卓.material:material:1.0.0'
    testImplementation 'junit:junit:4.12'
    安卓TestImplementation '安卓x.test.ext:junit:1.1.0'
    安卓TestImplementation '安卓x.test.espresso:espresso-core:3.1.1'
}

Answer 1

AndroidX replaces the original support library APIs with packages in the androidx namespace.

您正在使用androidx。所以添加androidx支持

 <item
    android:id="@+id/action_search"
    .....................
    app:actionViewClass="androidx.appcompat.widget.SearchView" />

并在下面的MainActivity部分导入

import androidx.appcompat.widget.SearchView;