Question

我已经创建了一个Android应用程序，其中aactivity打开另一个。打开的是：

package com.tendariuspro.oz;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Second extends Activity {

    Button btnYes;
    Button btnNo;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
    setContentView(R.layout.second);
    btnYes = (Button) findViewById (R.id.btnYesTwo);
    btnNo = (Button) findViewById (R.id.btnNoTwo);

    btnYes.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            try {
                Class<?> cc = Class.forName("com.tendariuspro.oz.Tenis");
                Intent ii = new Intent(Second.this, cc);
                startActivity(ii);
                finish();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    });

    btnNo.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            try {
                Class<?> c = Class.forName("com.tendariuspro.oz.Baschet");
                Intent i = new Intent(Second.this, c);
                startActivity(i);
                finish();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }


        }
    });


    }

}

和btnYes打开的那个是：

package com.tendariuspro.oz;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Baschet extends Activity{

    Button  btnYes;
    Button  btnNo;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
    setContentView(R.layout.baschet);

        btnYes = (Button) findViewById (R.id.btnYesOne);
        btnNo = (Button) findViewById (R.id.btnNoOne);

    btnYes.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            try {
                Class<?> cc = Class.forName("com.tendariuspro.oz.Razvan");
                Intent ii = new Intent(Baschet.this, cc);
                startActivity(ii);
                finish();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }
    });

    btnNo.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            try {
                Class<?> c = Class.forName("com.tendariuspro.oz.Rares");
                Intent i = new Intent(Baschet.this, c);
                startActivity(i);
                finish();
            } catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }

    });

    }


}

注意：btnNo打开的活动与此类似！

但是当我按下btnNo或btnYes时它会在第22行给出一个NullPointerException（btnYes）在这两个活动中！

你能帮帮我吗？

这是LogCat：

06-16 07:59:09.395: E/AndroidRuntime(1465): FATAL EXCEPTION: main
06-16 07:59:09.395: E/AndroidRuntime(1465): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tendariuspro.oz/com.tendariuspro.oz.Baschet}: java.lang.NullPointerException
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.os.Handler.dispatchMessage(Handler.java:99)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.os.Looper.loop(Looper.java:137)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.ActivityThread.main(ActivityThread.java:5041)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at java.lang.reflect.Method.invokeNative(Native Method)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at java.lang.reflect.Method.invoke(Method.java:511)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at dalvik.system.NativeStart.main(Native Method)
06-16 07:59:09.395: E/AndroidRuntime(1465): Caused by: java.lang.NullPointerException
06-16 07:59:09.395: E/AndroidRuntime(1465):     at com.tendariuspro.oz.Baschet.onCreate(Baschet.java:22)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.Activity.performCreate(Activity.java:5104)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
06-16 07:59:09.395: E/AndroidRuntime(1465):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
06-16 07:59:09.395: E/AndroidRuntime(1465):     ... 11 more

Answer 1

btnYes为空。

检查res / layut / baschet.xml以查看此按钮是否有id btnYesOne。

当我尝试使用Intent打开一个活动时出现NullPointerException

1 个答案: