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我正在尝试构建一个绘图应用程序。首先，我试图在屏幕上画一些东西，这是可行的。现在我正试着画一个圆圈来跟随我的手指。这在应用程序运行时不起作用，并且编译时没有错误或警告。出了什么问题，我该如何解决？

我认为onTouchEvent永远不会被调用。

我的视图类：

package gorrebeeck.david.dgor.eazydraw;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.drawable.ShapeDrawable;
import android.graphics.drawable.shapes.OvalShape;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;

public class CustomDrawableView extends View {
    private ShapeDrawable mDrawable;

    int x = 10;
    int y = 10;

    @Override
    public boolean onTouchEvent(MotionEvent e) {
        this.x=(int)e.getX();
        this.y=(int)e.getY();
        this.invalidate();
        return  true;
    }

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

        int width = 50;
        int height = 50;

        mDrawable = new ShapeDrawable(new OvalShape());
        mDrawable.getPaint().setColor(0xff74AC23);
        mDrawable.setBounds(x, y, x + width, y + height);
    }

    protected void onDraw(Canvas canvas) {
        mDrawable.draw(canvas);
    }
}

加载的类：

package gorrebeeck.david.dgor.eazydraw;

import android.content.Intent;
import android.graphics.Color;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;

import java.util.Random;

public class workspace extends AppCompatActivity {

    CustomDrawableView mCustomDrawableView;

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mCustomDrawableView = new CustomDrawableView(this);

        setContentView(mCustomDrawableView);

    }
}

运行时的警告：

06-21 16:05:14.834 2380-2543/gorrebeeck.david.dgor.eazydraw E/Surface:getSlotFromBufferLocked: unknown buffer: 0x7ffe7a162850
06-21 16:05:14.839 2380-2543/gorrebeeck.david.dgor.eazydraw D/OpenGLRenderer: endAllStagingAnimators on 0x7ffe71d90400 (RippleDrawable) with handle 0x7ffe71d1aac0
06-21 16:05:16.719 2380-2380/gorrebeeck.david.dgor.eazydraw W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=435.89355, y[0]=759.9121, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=63310, downTime=61173, deviceId=0, source=0x1002 }
06-21 16:05:16.719 2380-2380/gorrebeeck.david.dgor.eazydraw W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=435.89355, y[0]=759.9121, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=63310, downTime=61173, deviceId=0, source=0x1002 }
06-21 16:05:16.719 2380-2380/gorrebeeck.david.dgor.eazydraw W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=435.89355, y[0]=759.9121, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=63310, downTime=61173, deviceId=0, source=0x1002 }
06-21 16:05:16.719 2380-2380/gorrebeeck.david.dgor.eazydraw W/ViewRootImpl: Cancelling event due to no window focus: MotionEvent { action=ACTION_CANCEL, actionButton=0, id[0]=0, x[0]=435.89355, y[0]=759.9121, toolType[0]=TOOL_TYPE_FINGER, buttonState=0, metaState=0, flags=0x0, edgeFlags=0x0, pointerCount=1, historySize=0, eventTime=63310, downTime=61173, deviceId=0, source=0x1002 }
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1 回答 1

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这是一个样本，试试这个

public class MainActivity extends Activity {

DrawingView dv ;
private Paint mPaint;    

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    dv = new DrawingView(this);
    setContentView(dv);
    mPaint = new Paint();
    mPaint.setAntiAlias(true);
    mPaint.setDither(true);
    mPaint.setColor(Color.GREEN);
    mPaint.setStyle(Paint.Style.STROKE);
    mPaint.setStrokeJoin(Paint.Join.ROUND);
    mPaint.setStrokeCap(Paint.Cap.ROUND);
    mPaint.setStrokeWidth(12);
}

public class DrawingView extends View {

    public int width;
    public  int height;
    private Bitmap  mBitmap;
    private Canvas  mCanvas;
    private Path    mPath;
    private Paint   mBitmapPaint;
    Context context;
    private Paint circlePaint;
    private Path circlePath;

    public DrawingView(Context c) {
        super(c);
        context=c;
        mPath = new Path();
        mBitmapPaint = new Paint(Paint.DITHER_FLAG);
        circlePaint = new Paint();
        circlePath = new Path();
        circlePaint.setAntiAlias(true);
        circlePaint.setColor(Color.BLUE);
        circlePaint.setStyle(Paint.Style.STROKE);
        circlePaint.setStrokeJoin(Paint.Join.MITER);
        circlePaint.setStrokeWidth(4f);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        mBitmap = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        mCanvas = new Canvas(mBitmap);
    }

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

        canvas.drawBitmap( mBitmap, 0, 0, mBitmapPaint);
        canvas.drawPath( mPath,  mPaint);
        canvas.drawPath( circlePath,  circlePaint);
    }

    private float mX, mY;
    private static final float TOUCH_TOLERANCE = 4;

    private void touch_start(float x, float y) {
        mPath.reset();
        mPath.moveTo(x, y);
        mX = x;
        mY = y;
    }

    private void touch_move(float x, float y) {
        float dx = Math.abs(x - mX);
        float dy = Math.abs(y - mY);
        if (dx >= TOUCH_TOLERANCE || dy >= TOUCH_TOLERANCE) {
            mPath.quadTo(mX, mY, (x + mX)/2, (y + mY)/2);
            mX = x;
            mY = y;

            circlePath.reset();
            circlePath.addCircle(mX, mY, 30, Path.Direction.CW);
        }
    }

    private void touch_up() {
        mPath.lineTo(mX, mY);
        circlePath.reset();
        // commit the path to our offscreen
        mCanvas.drawPath(mPath,  mPaint);
        // kill this so we don't double draw
        mPath.reset();
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        float x = event.getX();
        float y = event.getY();

        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                touch_start(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_MOVE:
                touch_move(x, y);
                invalidate();
                break;
            case MotionEvent.ACTION_UP:
                touch_up();
                invalidate();
                break;
        }
        return true;
    }
}

}

首先浏览 sdk 示例中的 Fingerpaint 演示

于 2016-06-21T14:33:30.417 回答