我尝试为多个按钮创建一个onclicklistener，并采取以下错误
06-27 20:12:27.468: D/AndroidRuntime(4810): Shutting down VM
06-27 20:12:27.468: W/dalvikvm(4810): threadid=1: thread exiting with uncaught exception (group=0x415caba8)
06-27 20:12:27.468: E/AndroidRuntime(4810): FATAL EXCEPTION: main
06-27 20:12:27.468: E/AndroidRuntime(4810): Process: com.example.calculatorrr, PID: 4810
06-27 20:12:27.468: E/AndroidRuntime(4810): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.calculatorrr/com.example.calculatorrr.MainActivity}: java.lang.NullPointerException
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2233)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.ActivityThread.access$800(ActivityThread.java:135)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.os.Handler.dispatchMessage(Handler.java:102)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.os.Looper.loop(Looper.java:136)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.ActivityThread.main(ActivityThread.java:5001)
06-27 20:12:27.468: E/AndroidRuntime(4810): at java.lang.reflect.Method.invokeNative(Native Method)
06-27 20:12:27.468: E/AndroidRuntime(4810): at java.lang.reflect.Method.invoke(Method.java:515)
06-27 20:12:27.468: E/AndroidRuntime(4810): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
06-27 20:12:27.468: E/AndroidRuntime(4810): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
06-27 20:12:27.468: E/AndroidRuntime(4810): at dalvik.system.NativeStart.main(Native Method)
06-27 20:12:27.468: E/AndroidRuntime(4810): Caused by: java.lang.NullPointerException
06-27 20:12:27.468: E/AndroidRuntime(4810): at com.example.calculatorrr.MainActivity.onCreate(MainActivity.java:426)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.Activity.performCreate(Activity.java:5231)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
06-27 20:12:27.468: E/AndroidRuntime(4810): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2148)
06-27 20:12:27.468: E/AndroidRuntime(4810): ... 11 more
我的主要活动课程是：
public class MainActivity extends ActionBarActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if (savedInstanceState == null) {
getSupportFragmentManager().beginTransaction()
.add(R.id.container, new PlaceholderFragment()).commit();
}
FrameLayout mframelayout = (FrameLayout)findViewById(R.id.container);
Button mButton0 = (Button) mframelayout.findViewById(R.id.bt0);
Log.i("test1", mButton0.toString());
Button mButton1 = (Button) mframelayout.findViewById(R.id.bt1);
Button mButton2 = (Button) mframelayout.findViewById(R.id.bt2);
Button mButton3 = (Button) mframelayout.findViewById(R.id.bt3);
Button mButton4 = (Button) mframelayout.findViewById(R.id.bt4);
Button mButton5 = (Button) mframelayout.findViewById(R.id.bt5);
Button mButton6 = (Button) mframelayout.findViewById(R.id.bt6);
Button mButton7 = (Button) mframelayout.findViewById(R.id.bt7);
Button mButton8 = (Button) mframelayout.findViewById(R.id.bt8);
Button mButton9 = (Button) mframelayout.findViewById(R.id.bt9);
Button mButtonmul = (Button) mframelayout.findViewById(R.id.bt_multiplication);
Button mButtonplu = (Button) mframelayout.findViewById(R.id.bt_plus);
Button mButtonmin = (Button) mframelayout.findViewById(R.id.btminus);
Button mButtondiv = (Button) mframelayout.findViewById(R.id.bt_divide);
mButton0.setOnClickListener(onClickListener);
mButton1.setOnClickListener(onClickListener);
mButton2.setOnClickListener(onClickListener);
mButton3.setOnClickListener(onClickListener);
mButton4.setOnClickListener(onClickListener);
mButton5.setOnClickListener(onClickListener);
mButton6.setOnClickListener(onClickListener);
mButton7.setOnClickListener(onClickListener);
mButton8.setOnClickListener(onClickListener);
mButton9.setOnClickListener(onClickListener);
mButtonmul.setOnClickListener(onClickListener);
mButtonplu.setOnClickListener(onClickListener);
mButtonmin.setOnClickListener(onClickListener);
mButtondiv.setOnClickListener(onClickListener);
}
private View.OnClickListener onClickListener = new View.OnClickListener() {
@Override
public void onClick(View v) {
TextView txtview = (TextView) findViewById(R.id.txt1);
String message = txtview.getText().toString();
switch (v.getId()) {
case R.id.bt0:
message = message + "0";
break;
case R.id.bt1:
message = message + "1";
break;
case R.id.bt2:
message = message + "2";
break;
case R.id.bt3:
message = message + "3";
break;
case R.id.bt4:
message = message + "4";
break;
case R.id.bt5:
message = message + "5";
break;
case R.id.bt6:
message = message + "6";
break;
case R.id.bt7:
message = message + "7";
break;
case R.id.bt8:
message = message + "8";
break;
case R.id.bt9:
message = message + "9";
break;
case R.id.bt_multiplication:
message = message + "*";
break;
case R.id.bt_plus:
message = message + "+";
break;
case R.id.btminus:
message = message + "-";
break;
case R.id.bt_divide:
message = message + "/";
break;
}
txtview.setText(message);
}
};
}
我的两个资源文件是：
activity_main.xml中：
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.calculatorrr.MainActivity"
tools:ignore="MergeRootFrame" />
和fragment_main.xml：
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
>
<TextView
android:id="@+id/txt1"
android:layout_width="match_parent"
android:layout_height="66dp"
android:background="@android:color/darker_gray"
android:hint="0"
android:textSize="40dp" />
........ all the other butttons
我在谷歌搜索，这里按钮到目前为止没有任何作用！也许是显而易见的，我没有看到！谢谢你的关注！
编辑： 这是我得到错误的一行：
mButton0.setOnClickListener(onClickListener);
答案 0 :(得分：3)
在onClicklistener中，您的textview tx1为null，因为 textview txt1属于fragment而非activity_main。< / p>
所以要么在activity_main布局中使用tx1。或者使用onCreateView片段方法。
答案 1 :(得分：2)
您无法在活动中访问片段Button。所以请在里面只使用Fragment java类。你可以在PlaceholderFragment Fragment类中设置你的Button Click Listener而不是在activity
中