Java 我在使用setOnClickListener时出错
我让程序崩溃时，使用下面的简单代码，因为它是自动关闭后安装它Java 我在使用setOnClickListener时出错,java,android,eclipse,Java,Android,Eclipse,我让程序崩溃时，使用下面的简单代码，因为它是自动关闭后安装它 package com.zaki.thenewboston; import android.os.Bundle; import android.support.v4.app.Fragment; import android.support.v7.app.ActionBarActivity; import android.view.LayoutInflater; import android.view.Menu; import and
package com.zaki.thenewboston;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
int counter;
Button add,sub; //used to reference to xml view ids
TextView display; //used to reference to xml view ids
@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();
}
//zaki: this is to wait the R.layout.activity_main to load first other wise the program may crash
counter =0;
add = (Button) findViewById(R.id.bAdd);
// sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter ++;
display.setText("Your total is" + counter);
}
});
/*
sub.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter --;
display.setText("Your total is" + counter);
}
});*/
}
@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);
}
/**
* A placeholder fragment containing a simple view.
*/
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
return rootView;
}
}
}
09-21 12:58:37.277: D/AndroidRuntime(1449): Shutting down VM
09-21 12:58:37.277: W/dalvikvm(1449): threadid=1: thread exiting with uncaught exception (group=0xb2a81ba8)
09-21 12:58:37.277: E/AndroidRuntime(1449): FATAL EXCEPTION: main
09-21 12:58:37.277: E/AndroidRuntime(1449): Process: com.zaki.thenewboston, PID: 1449
09-21 12:58:37.277: E/AndroidRuntime(1449): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.zaki.thenewboston/com.zaki.thenewboston.MainActivity}: java.lang.NullPointerException
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.ActivityThread.access$800(ActivityThread.java:135)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.os.Handler.dispatchMessage(Handler.java:102)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.os.Looper.loop(Looper.java:136)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.ActivityThread.main(ActivityThread.java:5017)
09-21 12:58:37.277: E/AndroidRuntime(1449): at java.lang.reflect.Method.invokeNative(Native Method)
09-21 12:58:37.277: E/AndroidRuntime(1449): at java.lang.reflect.Method.invoke(Method.java:515)
09-21 12:58:37.277: E/AndroidRuntime(1449): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
09-21 12:58:37.277: E/AndroidRuntime(1449): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
09-21 12:58:37.277: E/AndroidRuntime(1449): at dalvik.system.NativeStart.main(Native Method)
09-21 12:58:37.277: E/AndroidRuntime(1449): Caused by: java.lang.NullPointerException
09-21 12:58:37.277: E/AndroidRuntime(1449): at com.zaki.thenewboston.MainActivity.onCreate(MainActivity.java:38)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.Activity.performCreate(Activity.java:5231)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
09-21 12:58:37.277: E/AndroidRuntime(1449): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
09-21 12:58:37.277: E/AndroidRuntime(1449): ... 11 more
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.zaki.thenewboston.MainActivity"
tools:ignore="MergeRootFrame" />
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/LinearLayout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.zaki.thenewboston.MainActivity$PlaceholderFragment" >
<TextView
android:id="@+id/tvDisplay"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/your_total_is" />
<Button
android:layout_width="240dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/add_one"
android:textSize="20sp"
android:id="@+id/bAdd"
/>
<Button
android:layout_width="240dp"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:text="@string/subtract_one"
android:textSize="20sp"
android:id="@+id/bSub"
/>
</LinearLayout>
问题仍然存在将其移动到片段类
counter =0;
add = (Button) rootView.findViewById(R.id.bAdd);
display = (TextView) rootView.findViewById(R.id.tvDisplay);
add.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
counter ++;
display.setText("Your total is" + counter);
}
});
我发现问题不仅仅在于在我得到一个新的代码时将代码移动到占位符片段 我发布的编译错误 还有下面的代码
add = (Button) findViewById (R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add = (Button) rootView.findViewById (R.id.bAdd);
sub = (Button) rootView.findViewById(R.id.bSub);
display = (TextView) rootView.findViewById(R.id.tvDisplay);
我很感谢对我所做的解释的评论复制粘贴它：-在课堂上张贴行号38粘贴布局文件活动\u main。我最好的猜测是布局文件缺少按钮。你的主XML文件是否有id=bAdd的按钮？@Nabin谢谢，这不是问题，我这样做时必须按Ctrl+k，我遇到以下错误无法从类型ActivityRemove static for placeholder Fragments对非静态方法FindViewByDint进行静态引用您似乎在代码格式方面有问题…不，不像我手动键入的部分代码
add = (Button) findViewById (R.id.bAdd);
sub = (Button) findViewById(R.id.bSub);
display = (TextView) findViewById(R.id.tvDisplay);
add = (Button) rootView.findViewById (R.id.bAdd);
sub = (Button) rootView.findViewById(R.id.bSub);
display = (TextView) rootView.findViewById(R.id.tvDisplay);