Android：将 CustomView 添加到 OnCreate

Question

我正在尝试添加一个自定义视图类以超出我的相机预览。

但我无法让它工作。即使只添加customview = new CustomView(this) 也不起作用。我收到错误：CustomView(com.example.android.camera2video.Camera2VideoFragment) CustomView 无法应用于 (com.example.android.camera2video.CameraAvticity)

这是我的代码，

CustomView.java

public class CustomView extends SurfaceView {

    private final Paint paint;
    private final SurfaceHolder mHolder;
    private final Context context;

    public CustomView(Camera2VideoFragment context) {
        super(context.getActivity().getBaseContext());
        mHolder = getHolder();
        mHolder.setFormat(PixelFormat.TRANSPARENT);
        this.context = context.getActivity().getBaseContext();
        paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.WHITE);
        paint.setStyle(Paint.Style.STROKE);

    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
            invalidate();
            if (mHolder.getSurface().isValid()) {
                final Canvas canvas = mHolder.lockCanvas();
                Log.d("touch", "touchRecieved by camera");
                if (canvas != null) {
                    Log.d("touch", "touchRecieved CANVAS STILL Not Null");
                    canvas.drawColor(Color.TRANSPARENT, PorterDuff.Mode.CLEAR);
                    canvas.drawColor(Color.TRANSPARENT);
                    canvas.drawCircle(event.getX(), event.getY(), 100, paint);
                    mHolder.unlockCanvasAndPost(canvas);
                    new Handler().postDelayed(new Runnable() {
                        @Override
                        public void run() {
                            Canvas canvas1 = mHolder.lockCanvas();
                            if(canvas1 !=null){
                                canvas1.drawColor(0, PorterDuff.Mode.CLEAR);
                                mHolder.unlockCanvasAndPost(canvas1);
                            }

                        }
                    }, 1000);

                }
                mHolder.unlockCanvasAndPost(canvas);


            }
        }


        return false;

CameraActivity.java

package com.example.android.camera2video;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;

public class CameraActivity extends Activity {
    private  Context context;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        customview = new CustomView(this);
        setContentView(R.layout.activity_camera);
        if (null == savedInstanceState) {
            getFragmentManager().beginTransaction()
                    .replace(R.id.container, Camera2VideoFragment.newInstance())
                    .commit();
        }
    }

}

Answer 1

构造函数允许在匹配 带有底层构造函数的 newInstance() 的实际参数 形式参数。所以一个类包含构造函数，这些构造函数被调用以从类蓝图创建对象。

不要

 public CustomView(Camera2VideoFragment context) 
   {
    super(context.getActivity().getBaseContext());  
    ........

您的 Constructor 期望 Activity Context instead of Fragment getactivity。

做

 public CustomView(Context context) {
 super(context);

仅供参考

如果在setContentView之后调用customview会更好。

    setContentView(R.layout.activity_camera);
    customview = new CustomView(this);

Answer 2

它不起作用，因为您的自定义视图构造函数采用 Camera2VideoFragment 类而不是活动。

public CustomView(Camera2VideoFragment context) {...}

当您调用new CustomView(this/* is Activity not Camera2VideoFragment */) 时，您正在传递一个Activity 实例，而它实际上需要Camera2VideoFragment。两者之间没有继承关系，因此会出现编译时错误。
要使其正常工作，您有 3 个选项：

1. 传递Camera2VideoFragment的实例
2. 将构造函数参数从Camera2VideoFragment改为Activity
3. 让你的活动扩展Camera2VideoFragment

Answer 3

您已通过customview = new CustomView(this); 创建了一个自定义视图，但您并未将此视图添加到您的布局中。您必须将此视图添加到您想要的位置。也许将它添加到您的根 ViewGroup。换句话说，您没有在任何地方使用过这个 customView，这就是它没有显示的原因。

将您的构造函数更改为此..

 public CustomView(Context context) {
    super(context);
    mHolder = getHolder();
    mHolder.setFormat(PixelFormat.TRANSPARENT);
    this.context = context;
    paint = new Paint(Paint.ANTI_ALIAS_FLAG);
    paint.setColor(Color.WHITE);
    paint.setStyle(Paint.Style.STROKE);

}

将其添加到您的根视图

final ViewGroup viewGroup = (ViewGroup) ((ViewGroup) this.findViewById(android.R.id.content)).getChildAt(0);
viewGroup.addView(new CustomView(this));