[英]my android app error unfortunately app has stopped
我是Android新手。
我刚刚开始构建我的第一个Android应用程序,并且在过去两天里一直在努力解决此错误。
没有找到解决方案,我不得不来到这里。
错误:
不幸的是“应用名称”已停止
这是主要的活动布局:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:text="TextView" />
</RelativeLayout>
这是另一种布局:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"></ListView>
</LinearLayout>
logcat错误
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.listview/com.example.listview.MainActivity}: java.lang.NullPointerException
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.ActivityThread.access$700(ActivityThread.java:135)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.os.Handler.dispatchMessage(Handler.java:102)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.os.Looper.loop(Looper.java:137)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.ActivityThread.main(ActivityThread.java:4998)
03-25 12:01:29.772: E/AndroidRuntime(1314): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 12:01:29.772: E/AndroidRuntime(1314): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 12:01:29.772: E/AndroidRuntime(1314): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
03-25 12:01:29.772: E/AndroidRuntime(1314): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
03-25 12:01:29.772: E/AndroidRuntime(1314): at dalvik.system.NativeStart.main(Native Method)
03-25 12:01:29.772: E/AndroidRuntime(1314): Caused by: java.lang.NullPointerException
03-25 12:01:29.772: E/AndroidRuntime(1314): at com.example.listview.MainActivity.onCreate(MainActivity.java:36)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.Activity.performCreate(Activity.java:5243)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-25 12:01:29.772: E/AndroidRuntime(1314): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
03-25 12:01:29.772: E/AndroidRuntime(1314): ... 11 more
03-25 12:01:35.622: I/Process(1314): Sending signal. PID: 1314 SIG: 9
03-25 12:11:56.522: D/AndroidRuntime(1378): Shutting down VM
03-25 12:11:56.522: W/dalvikvm(1378): threadid=1: thread exiting with uncaught exception (group=0xb3adbb90)
03-25 12:11:56.542: E/AndroidRuntime(1378): FATAL EXCEPTION: main
03-25 12:11:56.542: E/AndroidRuntime(1378): Process: com.example.listview, PID: 1378
03-25 12:11:56.542: E/AndroidRuntime(1378): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.listview/com.example.listview.MainActivity}: java.lang.NullPointerException
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.ActivityThread.access$700(ActivityThread.java:135)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.os.Handler.dispatchMessage(Handler.java:102)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.os.Looper.loop(Looper.java:137)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.ActivityThread.main(ActivityThread.java:4998)
03-25 12:11:56.542: E/AndroidRuntime(1378): at java.lang.reflect.Method.invokeNative(Native Method)
03-25 12:11:56.542: E/AndroidRuntime(1378): at java.lang.reflect.Method.invoke(Method.java:515)
03-25 12:11:56.542: E/AndroidRuntime(1378): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
03-25 12:11:56.542: E/AndroidRuntime(1378): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
03-25 12:11:56.542: E/AndroidRuntime(1378): at dalvik.system.NativeStart.main(Native Method)
03-25 12:11:56.542: E/AndroidRuntime(1378): Caused by: java.lang.NullPointerException
03-25 12:11:56.542: E/AndroidRuntime(1378): at com.example.listview.MainActivity.onCreate(MainActivity.java:36)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.Activity.performCreate(Activity.java:5243)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
03-25 12:11:56.542: E/AndroidRuntime(1378): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140)
03-25 12:11:56.542: E/AndroidRuntime(1378): ... 11 more
主要活动代码
package com.example.listview;
import java.util.ArrayList;
import java.util.Arrays;
import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ListView lst = (ListView)findViewById(R.id.listView1);
//ListView mainListView = null;
String[] test = new String[] { "Mercury", "Venus", "Earth", "Mars",
"Jupiter", "Saturn", "Uranus", "Neptune"};
ArrayList<String> planetList = new ArrayList<String>();
planetList.addAll( Arrays.asList(test) );
ArrayAdapter<String> listAdapter = new ArrayAdapter<String>(this, R.layout.simplerow, planetList);
// Add more planets. If you passed a String[] instead of a List<String>
// into the ArrayAdapter constructor, you must not add more items.
// Otherwise an exception will occur.
listAdapter.add( "Ceres" );
listAdapter.add( "Pluto" );
listAdapter.add( "Haumea" );
listAdapter.add( "Makemake" );
listAdapter.add( "Eris" );
// Set the ArrayAdapter as the ListView's adapter.
lst.setAdapter( listAdapter );
}
@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;
}
}
您的列表视图不包含在活动的布局中,因此当您调用它时,它将为您提供空指针异常。 您可以将listview放在主要活动的布局内。
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentRight="true"
android:text="TextView" />
<ListView
android:id="@+id/listView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"></ListView>
</RelativeLayout>
第36行是:
lst.setAdapter( listAdapter );
表示lst
可能为空。
ListView lst = (ListView)findViewById(R.id.listView1); //NULL
由于加载了main_activity
布局,该布局没有id=listView1
的ListView
,因此无法找到视图。
可能需要加载包含它的另一个布局。
ListView lst = (ListView)findViewById(R.id.listView1);
返回null,因为您没有在setContentView(R.layout.activity_main);
使用正确的内容setContentView(R.layout.activity_main);
。 您有两种选择:
使用include
将布局放入另一个布局中:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" ... > <TextView ... /> <include android:layout="@layout\\my_layout_listview" /> </RelativeLayout>
或设置包含您的ListView
的其他布局:
setContentView(R.layout.my_layout_listview);
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