Question

我正在尝试在不同位置创建相同的ImageView 20次，我正在使用此代码：

    rand = new Random();
    ImageView[] imageViewArray = new ImageView[20];
    ArrayList<Float> xarray = new ArrayList<>();
    ArrayList<Float> yarray = new ArrayList<>();
    Display display = getWindowManager().getDefaultDisplay();
    Point size = new Point();
    display.getSize(size);
    layoutwidth = size.x;
    layoutheight = size.y;
    Toast.makeText(MainActivity.this, " " + layoutwidth, Toast.LENGTH_SHORT).
            show();

    for (int i = 0; i < 20; i++) {
        imageViewArray[i] = new ImageView(this);
        imageViewArray[i].setTag(i);
        imageViewArray[i].setImageResource(R.mipmap.enemy);
        randx = rand.nextInt(layoutwidth + 1);
        randy = rand.nextInt(layoutheight + 1);
        imageViewArray[i].setX(randx);
        imageViewArray[i].setY(randy);
        xarray.add(imageViewArray[i].getX());
        yarray.add(imageViewArray[i].getY());
        rlt.addView(imageViewArray[i]);
    }

最终，我的应用程序在第rlt.addView(imageViewArray[i]);行崩溃并说它是一个空对象，这是我的logcat：

09-12 14:15:19.941  20395-20395/? E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: firstappdevelopment.thatdoskilledme, PID: 20395
    java.lang.RuntimeException: Unable to start activity ComponentInfo{firstappdevelopment.thatdoskilledme/firstappdevelopment.thatdoskilledme.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.addView(android.view.View)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3119)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3218)
            at android.app.ActivityThread.access$1000(ActivityThread.java:198)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1676)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:6837)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
            at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:115)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.addView(android.view.View)' on a null object reference
            at firstappdevelopment.thatdoskilledme.MainActivity.onCreate(MainActivity.java:56)
            at android.app.Activity.performCreate(Activity.java:6500)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1120)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3072)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3218)
            at android.app.ActivityThread.access$1000(ActivityThread.java:198)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1676)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:6837)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
            at de.robv.android.xposed.XposedBridge.main(XposedBridge.java:115)

我不知道为什么它会在for语句中创建它时返回null，有人可以帮助我，谢谢：）

Answer 1

确保正确声明相对布局。
您不必获取图像视图数组，因为所有元素都具有相同的位图，因此请定义包含图像视图的另一个xml文件，并且每次将该xml布局视图添加到相对布局！

ImageView Array返回null对象

1 个答案: