如何在Android中的自定义视图中显示ImageView

Question

我有一个活动，当按下按钮时调用自定义视图。自定义视图运行良好，直到我尝试向其添加 ImageView 为止。我已经在我的 xml 中尝试过此操作，该 xml 在我的主要活动中使用 setContentView 进行调用：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>

<com.mypackage.mycustomview android:id="@+id/fbv"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    >

        <ImageView android:id="@+id/pistolView"
              android:src="@drawable/pistol"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"/> 

</com.mypackage.mycustomview> 

当我单击主要活动中启动此自定义视图的按钮时，我收到 ClassCastException。我想做的就是在我的自定义视图中制作一个可点击的图像。

如果我将 ImageView 放入我的主要活动和 main.xml 中，它会显示良好并单击，如下所示：

<Button android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Play Vs CPU" />


        <ImageView android:id="@+id/pistolView"
              android:src="@drawable/pistol"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"/> 

我真的不擅长 android 中的 xml 布局，所以我不知道我在这里缺少什么。任何帮助是极大的赞赏。

这是 mycustomview 类：

       package com.mypackage;

    import java.util.ArrayList;

    import android.app.Activity;
    import android.content.Context;
    import android.content.res.Resources;
    import android.graphics.Bitmap;
    import android.graphics.BitmapFactory;
    import android.graphics.Canvas;
    import android.graphics.Paint;
    import android.graphics.Point;
    import android.graphics.drawable.Drawable;
    import android.os.Handler;
    import android.os.Message;
    import android.text.format.Time;
    import android.util.AttributeSet;
    import android.util.Log;
    import android.view.KeyEvent;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.widget.ImageView;
    import android.widget.LinearLayout;
    import android.widget.TextView;

    public class mycustomview extends View{
            final Paint mPaint = new Paint();
            private Context mContext;
            private Resources res = getResources();
            private GameControls _controls;
            private GameJoystick _joystick;
            private GameJoystick Rjoystick;
            Paint paint = new Paint();
            private long currTime;
            private Time time = new Time();
            private Hero mHero;
            private Gun mGun;
            private Bitmap heroBit;
            private float possibleX;
            private float possibleY;
            private float lazerX;
            private float lazerY;
            public ArrayList<Wall> wallList = new ArrayList<Wall>();
            private Canvas mCanvas;
            private Bitmap splat;
            private Bitmap pistolBit;
            private Bitmap building;
            private ImageView pistol;
            private int i = 0;
            private int w = 0;
            Wall wall;

            private RefreshHandler mRedrawHandler = new RefreshHandler();

        class RefreshHandler extends Handler {

            @Override
            public void handleMessage(Message msg) {
                    //Log.d("3", "here3");
                FanBoyView.this.update();
                FanBoyView.this.invalidate();
            }

            public void sleep(long delayMillis) {
                    this.removeMessages(0);
                sendMessageDelayed(obtainMessage(0), delayMillis);
            }
        };


        @Override
        public boolean onKeyDown(int keyCode, KeyEvent event) {
            //Log.d("-------------------->code", Integer.toString(keyCode));
            if (keyCode == KeyEvent.KEYCODE_FOCUS) {
                    //Log.d("-------------------->cam", "pressed");
              fireGun();
              return true;
            }
            return false;
         }

            public mycustomview(Context context, AttributeSet a) {
                    super(context, a);
                    mContext = context;

                    time.setToNow();
                    currTime = time.toMillis(false);
                    this.setFocusable(true);
                    this.setFocusableInTouchMode(true);
                    this.requestFocus();

                    final Paint paint = mPaint;
            paint.setColor(0xffffffff);
            paint.setAntiAlias(true);
            paint.setStrokeWidth(1);
            paint.setStrokeCap(Paint.Cap.ROUND);
            paint.setStyle(Paint.Style.STROKE);

                    setFocusable(true);

                    _joystick = new GameJoystick(mContext.getResources());
                    Rjoystick = new GameJoystick(mContext.getResources());
                    _controls = new GameControls();
                    setOnTouchListener(_controls);

                    Drawable bg = res.getDrawable(R.drawable.street);
                    this.setBackgroundDrawable(bg);
            setWalls();
            }

            @Override
            protected void  onFinishInflate(){
                    //ImageView img = (ImageView) findViewById(R.id.pistolView);
                    /*img.setOnClickListener(new OnClickListener() {
                        public void onClick(View v) {
                            Log.d("pistol","clicked");
                        }
                    });*/
            }
...

Answer 1

您收到 ClassCastException 因为视图不能有子视图，添加子视图适用于 ViewGroups http://developer.android.com/reference/android/view/ViewGroup.html

ImageView和TextView是普通视图，而LinearLayout和ListView是视图组。因此，后者可以有子视图，而前者则不能，这是有道理的。

您可以扩展 ViewGroup 而不是 View 并进行必要的调整，但在我看来，您应该使用相对布局，将自定义视图放在底部，将 imageview 放在顶部。