Android编程：控制器类中的按钮侦听器异常
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【中文标题】Android编程：控制器类中的按钮侦听器异常【英文标题】：Android programming : exception with button listener in controller class 【发布时间】：2017-08-26 02:50:27 【问题描述】：我有一个活动和一个按钮，通过单击我想打开另一个活动。我想在我的控制器类中执行按钮单击事件，所以我使用
在我的 MainActivity.java 中
MainController mainController = new MainController(btn_secondpage);
btn_secondpage.setOnClickListener(mainController);
在 MainController 类中我使用了这些方法-
在 MainController 类中..
public MainController(Button btn_secondpage)
this.btn_secondpage=btn_secondpage;
@Override
public void onClick(View v)
Intent intent = new Intent("com.testandroidproject.view.SecondActivity");
startActivity(intent);
但是，每当我单击按钮时，都会打开一个对话框并显示我的应用程序已停止工作... 我正在使用eclipse mars2 我已经提供了我所有的类，xml，manifest.xml
activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/layout_id"
style="@style/AppTheme"
android:layout_
android:layout_
android:focusable="false"
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="com.testandroidproject.view.MainActivity" >
<Button
android:id="@+id/btn_secondpage"
android:layout_
android:layout_
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Second page" />
</RelativeLayout>
activity_second.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_
android:layout_
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="com.testandroidproject.view.SecondActivity" >
<TextView
android:layout_
android:layout_
android:layout_centerHorizontal="true"
android:layout_centerVertical="true"
android:text="Welcome to second page" />
</RelativeLayout>
MainActivity.java
package com.testandroidproject.view;
import com.example.testandroidproject.R;
import com.testandroidproject.controller.MainController;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainActivity extends Activity
public Button btn_secondpage;
public static final String TAG = "abcd";
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Log.i(TAG, "inside oncreate"); // printing (1st)
btn_secondpage = (Button)findViewById(R.id.btn_secondpage);
MainController mainController = new MainController(btn_secondpage);
btn_secondpage.setOnClickListener(mainController);
// onButtonClick(); // this is working properly
////////////// this method is working properly.......
public void onButtonClick()
btn_secondpage = (Button)findViewById(R.id.btn_secondpage);
btn_secondpage.setOnClickListener(
new OnClickListener()
@Override
public void onClick(View v)
Intent intent = new Intent("com.testandroidproject.view.SecondActivity");
startActivity(intent);
);
@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)
// 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);
SecondActivity.java
package com.testandroidproject.view;
import com.example.testandroidproject.R;
import android.app.Activity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
public class SecondActivity extends Activity
@Override
protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_second);
@Override
public boolean onCreateOptionsMenu(Menu menu)
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.second, 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);
MainController.java
package com.testandroidproject.controller;
import android.app.Activity;
import android.content.Intent;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
public class MainController extends Activity implements OnClickListener
Button btn_secondpage;
public static final String TAG = "abcd";
public MainController(Button btn_secondpage)
this.btn_secondpage=btn_secondpage;
Log.i(TAG, "inside mainController constructor"); // printing (2nd)
@Override
public void onClick(View v)
Log.i(TAG, "inside public void onClick before intent"); // printing(3rd)
Intent intent = new Intent("com.testandroidproject.view.SecondActivity");
Log.i(TAG, "inside public void onClick after intent"); // printing(4th)
startActivity(intent);
Log.i(TAG, "inside public void onClick after startActivity"); // NOT printing
AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.testandroidproject"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="21"
android:targetSdkVersion="21" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name="com.testandroidproject.view.MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity
android:name="com.testandroidproject.view.SecondActivity"
android:label="@string/title_activity_second" >
<intent-filter>
<action android:name="com.testandroidproject.view.SecondActivity" />
<category android:name="android.intent.category.DEFAULT" />
</intent-filter>
</activity>
</application>
</manifest>
日志猫
04-01 00:10:38.344: I/abcd(1764): inside oncreate
04-01 00:10:38.345: I/abcd(1764): inside mainController constructor
04-01 00:10:38.370: D/OpenGLRenderer(1764): Render dirty regions requested: true
04-01 00:10:38.374: D/(1764): HostConnection::get() New Host Connection established 0xa5f43380, tid 1764
04-01 00:10:38.375: D/Atlas(1764): Validating map...
04-01 00:10:38.399: D/(1764): HostConnection::get() New Host Connection established 0xad480dc0, tid 1780
04-01 00:10:38.401: I/OpenGLRenderer(1764): Initialized EGL, version 1.4
04-01 00:10:38.446: D/OpenGLRenderer(1764): Enabling debug mode 0
04-01 00:10:38.546: W/EGL_emulation(1764): eglSurfaceAttrib not implemented
04-01 00:10:38.546: W/OpenGLRenderer(1764): Failed to set EGL_SWAP_BEHAVIOR on surface 0xa5f46240, error=EGL_SUCCESS
04-01 00:11:51.749: I/abcd(1764): inside oncreate
04-01 00:11:51.754: I/abcd(1764): inside mainController constructor
04-01 00:11:51.896: W/EGL_emulation(1764): eglSurfaceAttrib not implemented
04-01 00:11:51.896: W/OpenGLRenderer(1764): Failed to set EGL_SWAP_BEHAVIOR on surface 0xa5f46240, error=EGL_SUCCESS
04-01 00:11:55.658: I/abcd(1764): inside public void onClick before intent
04-01 00:11:55.658: I/abcd(1764): inside public void onClick after intent
04-01 00:11:55.658: D/AndroidRuntime(1764): Shutting down VM
04-01 00:11:55.658: D/AndroidRuntime(1764): --------- beginning of crash
04-01 00:11:55.658: E/AndroidRuntime(1764): FATAL EXCEPTION: main
04-01 00:11:55.658: E/AndroidRuntime(1764): Process: com.example.testandroidproject, PID: 1764
04-01 00:11:55.658: E/AndroidRuntime(1764): java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.ActivityThread$ApplicationThread android.app.ActivityThread.getApplicationThread()' on a null object reference
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.app.Activity.startActivityForResult(Activity.java:3736)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android. app.Activity.startActivityForResult(Activity.java:3697)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.app.Activity.startActivity(Activity.java:4007)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.app.Activity.startActivity(Activity.java:3975)
04-01 00:11:55.658: E/AndroidRuntime(1764): at com.testandroidproject.controller.MainController.onClick(MainController.java:24)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.view.View.performClick(View.java:4756)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.view.View$PerformClick.run(View.java:19749)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.os.Handler.handleCallback(Handler.java:739)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.os.Handler.dispatchMessage(Handler.java:95)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.os.Looper.loop(Looper.java:135)
04-01 00:11:55.658: E/AndroidRuntime(1764): at android.app.ActivityThread.main(ActivityThread.java:5221)
04-01 00:11:55.658: E/AndroidRuntime(1764): at java.lang.reflect.Method.invoke(Native Method)
04-01 00:11:55.658: E/AndroidRuntime(1764): at java.lang.reflect.Method.invoke(Method.java:372)
04-01 00:11:55.658: E/AndroidRuntime(1764): at com.and roid.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
04-01 00:11:55.658: E/AndroidRuntime(1764): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
04-01 00:11:55.857: I/art(1764): Background sticky concurrent mark sweep GC freed 2383(175KB) AllocSpace objects, 1(81KB) LOS objects, 29% free, 794KB/1135KB, paused 1.621ms total 150.498ms
04-01 00:12:09.406: I/Process(1764): Sending signal. PID: 1764 SIG: 9
enter image description here
【问题讨论】：
欢迎堆栈溢出！请向我们展示您的错误日志。 嗨，是的，我刚刚提供了我的 LogCat。请检查一下。 【参考方案1】：在onClick() 中的MainController 类中创建Intent 对象时是错误的，请使用此Intent intent = new Intent(btn_secondpage.getContext(), SecondActivity.class); 进行更改
确保您的 MainController 不是 Activity 的子类，这会导致错误。因为现在你的activity不是Context的子类，所以不能调用startActivity()。要启动一个活动，请使用传递的 Button 的上下文
public class MainController implements OnClickListener
//............
@Override
public void onClick(View v)
Intent intent = new Intent(btn_secondpage.getContext(), SecondActivity.class);
btn_secondpage.getContext().startActivity(intent);
【讨论】：
非常感谢，这次运行正常。感谢您的时间和耐心。以上是关于Android编程：控制器类中的按钮侦听器异常的主要内容，如果未能解决你的问题，请参考以下文章
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