Question

我刚刚实现了onClickListener。应用程序应在两个布局之间切换。每个布局都有一个按钮。触摸按钮后，布局应该更改。

我搜索了各种教程和纪录片，我的代码应该是正确的，我根本看不到错误。 Eclipse也说代码没问题。

    package ralationship.v1;

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

public class RelationshipActivity extends Activity implements OnClickListener{
    /** Called when the activity is first created. */
    private Button OptionsButton;
    private Button SaveButton;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        SaveButton = (Button)findViewById(R.id.btnSave);
        OptionsButton = (Button)findViewById(R.id.btnOptions);
        OptionsButton.setOnClickListener(this);
        SaveButton.setOnClickListener(this);

    }

    public void onClick(View v) {
        if(v.getId() == (R.id.btnOptions)){
            setContentView(R.layout.options);
        }else if (v.getId() == (R.id.btnSave)){
            setContentView(R.layout.main);
        }

    }

}

有没有人发现错误？

//编辑：

以下是LogCat报告：

01-26 15:47:29.273: D/dalvikvm(336): GC_EXTERNAL_ALLOC freed 49K, 53% free 2549K/5379K, external 1625K/2137K, paused 67ms
01-26 15:47:29.453: D/AndroidRuntime(336): Shutting down VM
01-26 15:47:29.462: W/dalvikvm(336): threadid=1: thread exiting with uncaught exception (group=0x40015560)
01-26 15:47:29.473: E/AndroidRuntime(336): FATAL EXCEPTION: main
01-26 15:47:29.473: E/AndroidRuntime(336): java.lang.RuntimeException: Unable to start activity ComponentInfo{ralationship.v1/ralationship.v1.RelationshipActivity}: java.lang.NullPointerException
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1647)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.os.Handler.dispatchMessage(Handler.java:99)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.os.Looper.loop(Looper.java:123)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.ActivityThread.main(ActivityThread.java:3683)
01-26 15:47:29.473: E/AndroidRuntime(336):  at java.lang.reflect.Method.invokeNative(Native Method)
01-26 15:47:29.473: E/AndroidRuntime(336):  at java.lang.reflect.Method.invoke(Method.java:507)
01-26 15:47:29.473: E/AndroidRuntime(336):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
01-26 15:47:29.473: E/AndroidRuntime(336):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
01-26 15:47:29.473: E/AndroidRuntime(336):  at dalvik.system.NativeStart.main(Native Method)
01-26 15:47:29.473: E/AndroidRuntime(336): Caused by: java.lang.NullPointerException
01-26 15:47:29.473: E/AndroidRuntime(336):  at ralationship.v1.RelationshipActivity.onCreate(RelationshipActivity.java:22)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
01-26 15:47:29.473: E/AndroidRuntime(336):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1611)
01-26 15:47:29.473: E/AndroidRuntime(336):  ... 11 more
01-26 15:47:33.633: I/Process(336): Sending signal. PID: 336 SIG: 9

Answer 1

如果选项按钮位于选项xml中，则必须手动充气。当你调用setContentView并分配一个布局xml时，你可以自动从该特定xml上的内容中膨胀。如果你需要充气，你必须使用layoutInflater context.getSystemService（context.layoutInflaterservice）

在将内容视图设置为

之前，基本上不会实例化选项按钮

Answer 2

我认为您的saveButton位于R.layout.options布局中？如果是，则首次创建活动时无法找到，因为您只有R.layout.main的内容。你应该改为行

SaveButton = (Button)findViewById(R.id.btnSave);
SaveButton.setOnClickListener(this);

将onClickListener的布局更改为正确的布局后，在setContentLayout()内的

。

应用程序在实现onClickListener后崩溃

2 个答案: