在位图图像上设置onClickListener会产生错误。

Question

我开始在我的安卓游戏（flappy bird类型的克隆游戏）中实现触摸控制，但我很难做到这一点。我已经实现了onTouchEvent，基本上可以覆盖整个屏幕，并对任何触摸做出反应，但现在我想在此基础上扩展，并拥有可点击的buttonicons等。我了解到OnClickListener函数应该可以完成这项工作，但我在这个问题上被卡住了，现在游戏在初始化后就崩溃了。

根据我的研究，我已经把我的playbutton(PNG图片)设置为ImageBitmap，然后把它设置为OnClickListener，目前我只是测试一下，给我一些东西来安慰。在MainActivity中，我也按照建议设置了ImageButton的findViewById。在Android Studio中没有出错，但运行后会出现这个情况。

2020-05-11 21:23:34.526 6075-6075/com.markS.flappykillercrow E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.markS.flappykillercrow, PID: 6075
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.markS.flappykillercrow/com.markS.flappykillercrow.MainActivity}: android.view.InflateException: Binary XML file line #9: Binary XML file line #9: Error inflating class com.markS.flappykillercrow.GameManager
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2778)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: android.view.InflateException: Binary XML file line #9: Binary XML file line #9: Error inflating class com.markS.flappykillercrow.GameManager
     Caused by: android.view.InflateException: Binary XML file line #9: Error inflating class com.markS.flappykillercrow.GameManager
     Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Constructor.newInstance0(Native Method)
        at java.lang.reflect.Constructor.newInstance(Constructor.java:334)
        at android.view.LayoutInflater.createView(LayoutInflater.java:647)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:790)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
        at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:419)
        at android.app.Activity.setContentView(Activity.java:2669)
        at com.markS.flappykillercrow.MainActivity.onCreate(MainActivity.java:24)
        at android.app.Activity.performCreate(Activity.java:7009)
        at android.app.Activity.performCreate(Activity.java:7000)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856)
        at android.app.ActivityThread.-wrap11(Unknown Source:0)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:164)
        at android.app.ActivityThread.main(ActivityThread.java:6494)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setImageBitmap(android.graphics.Bitmap)' on a null object reference
        at com.markS.flappykillercrow.sprites.GameOver.<init>(GameOver.java:33)
        at com.markS.flappykillercrow.GameManager.initGame(GameManager.java:86)
        at com.markS.flappykillercrow.GameManager.<init>(GameManager.java:75)
        at java.lang.reflect.Constructor.newInstance0(Native Method) 
        at java.lang.reflect.Constructor.newInstance(Constructor.java:334) 
        at android.view.LayoutInflater.createView(LayoutInflater.java:647) 
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:790) 
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730) 
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:863) 
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824) 
        at android.view.LayoutInflater.inflate(LayoutInflater.java:515) 
        at android.view.LayoutInflater.inflate(LayoutInflater.java:423) 
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374) 
        at com.android.internal.policy.PhoneWindow.setContentView(PhoneWindow.java:419) 
        at android.app.Activity.setContentView(Activity.java:2669) 
        at com.markS.flappykillercrow.MainActivity.onCreate(MainActivity.java:24) 
        at android.app.Activity.performCreate(Activity.java:7009) 
        at android.app.Activity.performCreate(Activity.java:7000) 
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1214) 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2731) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2856) 
        at android.app.ActivityThread.-wrap11(Unknown Source:0) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1589) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.app.ActivityThread.main(ActivityThread.java:6494) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:438) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:807) 

这里是我用OnClickListener实现playbutton的类:

package com.markS.flappykillercrow.sprites;

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.view.View;
import android.widget.ImageButton;
import android.widget.Toast;

import com.markS.flappykillercrow.MainActivity;
import com.markS.flappykillercrow.R;

public class GameOver implements Sprite {
    private Bitmap gameOver;
    private Bitmap playButton;   //adding playButton Bitmap
    private Bitmap rateUs;
    private Bitmap volumeOn;
    private Bitmap volumeOf;
    private ImageButton imgButton;

    private int screenHeight, screenWidth;

    public GameOver(Resources resources, int screenHeight, int screenWidth) {
        this.screenHeight = screenHeight;
        this.screenWidth = screenWidth;
        gameOver = BitmapFactory.decodeResource(resources, R.drawable.gameover);

        playButton = BitmapFactory.decodeResource(resources, R.drawable.playbutton);
        imgButton.setImageBitmap(playButton);
        imgButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                System.out.println("THIS WORKS");
            }
        });

        rateUs = BitmapFactory.decodeResource(resources, R.drawable.rateus);
        volumeOn = BitmapFactory.decodeResource(resources, R.drawable.volumeon);
        volumeOf = BitmapFactory.decodeResource(resources, R.drawable.volumeoff);
    }

    @Override
    public void draw(Canvas canvas) {
        canvas.drawBitmap(gameOver, screenWidth / 2 - gameOver.getWidth() / 2, screenHeight / 4, null);
    }

    //for drawing playbutton
    public void drawplay(Canvas canvas) {
        canvas.drawBitmap(playButton, (screenWidth / 2 - playButton.getWidth() / 2), screenHeight / (float) 2.5, null);
    }

    //for drawing rate us
    public void drawrateus(Canvas canvas) {
        canvas.drawBitmap(rateUs, (float) (screenWidth / 1.4 - rateUs.getWidth() / 21.7), screenHeight / (float) 3.2, null);
    }

    //for drawing volumes
    public void drawvolumeon(Canvas canvas) {
        canvas.drawBitmap(volumeOn, (screenWidth / 23 - volumeOn.getWidth() / 23), screenHeight / 50, null);
    }

    //later implement if statement
    public void drawvolumeof(Canvas canvas) {
        canvas.drawBitmap(volumeOf, (screenWidth / 20 - volumeOf.getWidth() / 20), screenHeight / 50, null);
    }

    @Override
    public void update() {
    }
}

MainActivity:

package com.markS.flappykillercrow;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Activity;
import android.os.Bundle;
import android.view.Window;
import android.widget.ImageButton;

import com.google.android.gms.ads.AdRequest;
import com.google.android.gms.ads.AdView;
import com.google.android.gms.ads.MobileAds;

public class MainActivity extends Activity {
    private AdView nAdView;
    private ImageButton imgButton;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        requestWindowFeature(Window.FEATURE_NO_TITLE);

        setContentView(R.layout.activity_main);
        imgButton=(ImageButton) findViewById(R.id.imgButton);

        MobileAds.initialize(this,"ca-app-pub-9057526686789846~7828440247"); //just a test ID
        nAdView=findViewById(R.id.adView);
        AdRequest adRequest=new AdRequest.Builder().build();
        nAdView.loadAd(adRequest);
    }
}

谢谢你们的任何有用的建议。我想一旦我把那个 "sout "转到console工作，我可以从那里进行管理，但现在我只是卡了太长时间。谢谢你们!

Answer 1

你的回溯中的相关（原始）错误。

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setImageBitmap(android.graphics.Bitmap)' on a null object reference

你需要初始化 imgButton.