Android OnClickListener 不工作 [重复]

Question

我写了一个简单的代码来添加两个数字。但是每当我使用按钮 OnClickListener() 函数时，应用程序就会崩溃。

import android.support.v7.app.ActionBarActivity;
import android.widget.Button;
import android.widget.TextView;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;


public class MainActivity extends ActionBarActivity {
    Button button1; 
    EditText txtbox1,txtbox2; 
    TextView tv; 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        txtbox1 = (EditText) findViewById(R.id.editText1);
        txtbox2 = (EditText) findViewById(R.id.editText2);
        button1 = (Button) findViewById(R.id.button1);
        tv = (TextView) findViewById(R.id.textView1);
        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
        }

    button1.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) { 
        String a,b; 
                    Integer vis; 
                    a = txtbox1.getText().toString(); 
                    b = txtbox2.getText().toString(); 
                    vis = Integer.parseInt(a)+Integer.parseInt(b); 
                    tv.setText(vis.toString()); 
            }
    });
}

所以为了检查出了什么问题，我将 button1.setOnClickListener 中的代码更改为一个简单的，只是将 textview 更改为一些随机文本。应用程序仍然崩溃。所以我想问题只出在我的按钮功能上。

这也是我的 xml 文件。

<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:background="#FFFFFF"
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.example.chawla.MainActivity$PlaceholderFragment" >

<EditText
    android:id="@+id/editText1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:hint="@string/edit_text1"
     />

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/editText1"
    android:layout_below="@+id/editText1"
    android:layout_marginTop="81dp"
    android:text="@string/button_text" 
    android:clickable="true"
    />

<EditText
    android:id="@+id/editText2"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/editText1"
    android:layout_below="@+id/editText1"
    android:layout_marginTop="18dp"
    android:ems="10"
    android:hint="@string/edit_text2" />

<TextView
    android:id="@+id/textView1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_below="@+id/button1"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="98dp"
    android:text="hi" />

这是堆栈跟踪

06-04 18:24:35.150: E/AndroidRuntime(12289): FATAL EXCEPTION: main
06-04 18:24:35.150: E/AndroidRuntime(12289): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.chawla/com.example.chawla.MainActivity}: java.lang.NullPointerException
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2304)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2354)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.ActivityThread.access$600(ActivityThread.java:153)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.os.Looper.loop(Looper.java:137)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.ActivityThread.main(ActivityThread.java:5228)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at java.lang.reflect.Method.invokeNative(Native Method)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at java.lang.reflect.Method.invoke(Method.java:511)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:794)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:561)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at dalvik.system.NativeStart.main(Native Method)
06-04 18:24:35.150: E/AndroidRuntime(12289): Caused by: java.lang.NullPointerException
06-04 18:24:35.150: E/AndroidRuntime(12289):    at com.example.chawla.MainActivity.onCreate(MainActivity.java:35)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.Activity.performCreate(Activity.java:5213)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
06-04 18:24:35.150: E/AndroidRuntime(12289):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2258)
06-04 18:24:35.150: E/AndroidRuntime(12289):    ... 11 more

提前致谢

Answer 1

如果你在你的类中实现你自己的 OnclickListener，你应该从 xml 中删除这一行：

      android:clickable="true"

我遇到了同样的问题，这是主要原因。