列表视图使 android 应用程序崩溃

Question

我正在开发一个与健康相关的安卓应用。在此，我使用 IndexPage.java 中的浮动操作按钮切换到另一个活动 FoodEntry.java（具有食品列表视图）。在这种情况下，每当我们单击浮动按钮时，应用程序就会崩溃。我发现的一件事是应用程序由于列表视图而崩溃。请帮助我找到解决方案。

这是 IndexPage.java

public class IndexPage extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_index_page);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

           Intent in = new Intent(IndexPage.this, FoodEntry.class);
            startActivity(in);

        }
    });
}
}

FoodEntry.java

public class FoodEntry extends AppCompatActivity {

// Array of strings...
String[] food = {"Naan","Pav bhaji","chole tikiya", "rice", "soyabean", "milk", "curd", "abc", "def", "dfadf", "fasdfa", "fsadf", "fdsfa", "fga"};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);


    ArrayAdapter adapter = new ArrayAdapter<>(this, R.layout.activity_item, food);
    ListView listViewFoodItems = (ListView)findViewById(R.id.listViewFood);
    listViewFoodItems.setAdapter(adapter);
} }

logcat 错误

03-31 15:30:58.555 13732-13732/com.praval.healthfreak W/dalvikvm: threadid=1: calling UncaughtExceptionHandler
03-31 15:30:58.556 13732-13732/com.praval.healthfreak E/AndroidRuntime: FATAL EXCEPTION: main
                                                                        Process: com.praval.healthfreak, PID: 13732
                                                                        java.lang.RuntimeException: Unable to start activity ComponentInfo{com.praval.healthfreak/com.praval.healthfreak.FoodEntry}: java.lang.NullPointerException
                                                                            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2389)
                                                                            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441)
                                                                            at android.app.ActivityThread.access$900(ActivityThread.java:151)
                                                                            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354)
                                                                            at android.os.Handler.dispatchMessage(Handler.java:110)
                                                                            at android.os.Looper.loop(Looper.java:193)
                                                                            at android.app.ActivityThread.main(ActivityThread.java:5345)
                                                                            at java.lang.reflect.Method.invokeNative(Native Method)
                                                                            at java.lang.reflect.Method.invoke(Method.java:515)
                                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828)
                                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644)
                                                                            at dalvik.system.NativeStart.main(Native Method)
                                                                         Caused by: java.lang.NullPointerException
                                                                            at com.praval.healthfreak.FoodEntry.onCreate(FoodEntry.java:20)
                                                                            at android.app.Activity.performCreate(Activity.java:5343)
                                                                            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1088)
                                                                            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2343)
                                                                            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2441) 
                                                                            at android.app.ActivityThread.access$900(ActivityThread.java:151) 
                                                                            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1354) 
                                                                            at android.os.Handler.dispatchMessage(Handler.java:110) 
                                                                            at android.os.Looper.loop(Looper.java:193) 
                                                                            at android.app.ActivityThread.main(ActivityThread.java:5345) 
                                                                            at java.lang.reflect.Method.invokeNative(Native Method) 
                                                                            at java.lang.reflect.Method.invoke(Method.java:515) 
                                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:828) 
                                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:644) 
                                                                            at dalvik.system.NativeStart.main(Native Method)

Answer 1

你忘了添加

setContentView(R.layout.activity_layout);

在FoodEntry Activity