Question

my java class consists of following code
package com.example.sati;

import com.example.sati.R;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {
int count;
Button add,sub;
TextView display;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    count=0;
    add=(Button)findViewById(R.id.but);
    sub=(Button)findViewById(R.id.butone);
    display=(Button)findViewById(R.id.tvdis);
sub.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
             count++;
             display.setText("your total is"+count);
        }
    });
    sub.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            count--;
             display.setText("your total is"+count);
        }
    });


}


@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;
}

}

我的xml文件代码如下;

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
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:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:text="@string/hello_world"
    android:layout_gravity="center" 
    android:gravity="center"
    android:id="@+id/tvdis"
    />

<Button
    android:layout_width="250dp"
    android:layout_height="wrap_content"
    android:text="@string/tot"
    android:textSize="25sp" 
    android:layout_gravity="center"
    android:id="@+id/but"/>
<Button
    android:layout_width="250dp"
    android:layout_height="wrap_content"
    android:text="@string/tet"
    android:textSize="25sp"
    android:layout_gravity="center"
    android:id="@+id/butone" />

</LinearLayout>

但是当我运行此应用程序时，它会显示消息“您的应用程序sati已意外停止。请在模拟器上再次尝试[强制关闭]。

Log cat显示以下错误;

03-23 01:10:30.042: D/AndroidRuntime(476): Shutting down VM
03-23 01:10:30.042: W/dalvikvm(476): threadid=1: thread exiting with uncaught exception   (group=0x4001d800)
03-23 01:10:30.072: E/AndroidRuntime(476): FATAL EXCEPTION: main
03-23 01:10:30.072: E/AndroidRuntime(476): java.lang.RuntimeException: Unable to start    activity ComponentInfo{com.example.sati/com.example.sati.MainActivity}:     java.lang.ClassCastException: android.widget.TextView
03-23 01:10:30.072: E/AndroidRuntime(476):  at  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
03-23 01:10:30.072: E/AndroidRuntime(476):  at   android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
03-23 01:10:30.072: E/AndroidRuntime(476):  at  android.app.ActivityThread.access$2300(ActivityThread.java:125)
03-23 01:10:30.072: E/AndroidRuntime(476):  at  android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
03-23 01:10:30.072: E/AndroidRuntime(476):  at  android.os.Handler.dispatchMessage(Handler.java:99)
03-23 01:10:30.072: E/AndroidRuntime(476):  at android.os.Looper.loop(Looper.java:123)
03-23 01:10:30.072: E/AndroidRuntime(476):  at android.app.ActivityThread.main(ActivityThread.java:4627)
03-23 01:10:30.072: E/AndroidRuntime(476):  at java.lang.reflect.Method.invokeNative(Native Method)
03-23 01:10:30.072: E/AndroidRuntime(476):  at  java.lang.reflect.Method.invoke(Method.java:521)
03-23 01:10:30.072: E/AndroidRuntime(476):  at  com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
03-23 01:10:30.072: E/AndroidRuntime(476):  at  com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
03-23 01:10:30.072: E/AndroidRuntime(476):  at dalvik.system.NativeStart.main(NativeMethod)

//应用程序包含两个按钮add和sub在按下时添加1加上当按下sub时减去一个，并且数字的增量和减少显示为按钮上方的文本

03-23 01:10:30.072: E/AndroidRuntime(476): Caused by: java.lang.ClassCastException: android.widget.TextView
03-23 01:10:30.072: E/AndroidRuntime(476):  at          com.example.sati.MainActivity.onCreate(MainActivity.java:26)
03-23 01:10:30.072: E/AndroidRuntime(476):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)   
03-23 01:10:30.072: E/AndroidRuntime(476):  at  android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
03-23 01:10:30.072: E/AndroidRuntime(476):  ... 11 more
03-23 01:15:30.154: I/Process(476): Sending signal. PID: 476 SIG: 9

Answer 1

display=(Button)findViewById(R.id.tvdis);

应该是

display=(TextView)findViewById(R.id.tvdis);

您将其声明为TextView但尝试将其转换为Button。这是您的例外Caused by: java.lang.ClassCastException: android.widget.TextView

同时删除setContentView和onCreate的一次通话。无需再打两次电话。

应用程序sati（进程com.example.sati）意外停止。请再试一次。[强制关闭]

1 个答案: