Android draw onAttachToWindow
package zzx.lly.custom_view.view;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.os.AsyncTask;import android.util.AttributeSet;import android.util.Log;import android.view.View;import zzx.lly.custom_view.R;public class Change_view extends View { //process determine the stage of this view that should be draw private int process; private Paint mPaint1; private int colorBegin; private int colorEnd=0; //在java代码则调用该构造方法 public Change_view(Context context) { super(context); init(); } //在xml调用时调用 public Change_view(Context context, AttributeSet attrs) { this(context, attrs, 0); init(); } //不会自动调用,一般是在第二个构造方法里面主动调用,如view有style属性时候 public Change_view(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.Change_view); colorBegin = a.getColor(R.styleable.Change_view_circle_color, Color.RED); a.recycle(); colorEnd=colorBegin; init(); } public Change_view(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) { super(context, attrs, defStyleAttr, defStyleRes); } private void init() { mPaint1 = new Paint(); mPaint1.setColor(colorEnd); mPaint1.setStrokeWidth(5f); mPaint1.setStyle(Paint.Style.FILL_AND_STROKE); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); mPaint1.setColor(colorEnd); int width = getWidth(); int height = getHeight(); int r = Math.min(width, height) / 2; canvas.drawCircle(width / 2, height / 2, r, mPaint1); Log.e("E", "draw"); } @Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { super.onMeasure(widthMeasureSpec, heightMeasureSpec); int widthMode = MeasureSpec.getMode(widthMeasureSpec); int widthSize = MeasureSpec.getSize(widthMeasureSpec); int heightMode = MeasureSpec.getMode(heightMeasureSpec); int heightSize = MeasureSpec.getSize(heightMeasureSpec); int mWidth = 400; int mHeight = 400; if (widthMode == MeasureSpec.AT_MOST && heightMode == MeasureSpec.AT_MOST) { setMeasuredDimension(mWidth, mHeight); } else if (widthMode == MeasureSpec.AT_MOST) { setMeasuredDimension(mWidth, heightSize); } else if (heightMode == MeasureSpec.AT_MOST) { setMeasuredDimension(widthSize, mHeight); } } //接下来实现异步变换颜色,1,通过Async或者rxjava class ColorChangeAsycTask extends AsyncTask<Void, Void, Void> { @Override protected void onPreExecute(){ super.onPreExecute(); colorEnd=colorBegin; } @Override //Result params protected Void doInBackground(Void... voids) { while(true){ colorEnd-=20; Log.e("E","colorChange"); if (colorEnd <= colorBegin/2) { colorEnd=colorBegin; } try { Thread.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); } publishProgress(); } } @Override //Result protected void onPostExecute(Void m) { super.onPostExecute(m); } @Override //progress protected void onProgressUpdate(Void... m) { invalidate(); } } @Override//为了避免错误,我们在这里将Async new出来并实现,因为在构造方法中界面不一定初始完成 protected void onAttachedToWindow() { Log.e("E", "beforeOnAttach"); super.onAttachedToWindow(); Log.e("E", "AfterOnAttach"); new ColorChangeAsycTask().execute(); Log.e("E", "onAttach"); }}Log日志 |11-23 21:53:24.263 11194-11194/zzx.lly.custom_view E/E:
beforeOnAttach
AfterOnAttach 11-23 21:53:24.265 11194-11194/zzx.lly.custom_view E/E: onAttach 11-23 21:53:24.266 11194-11220/zzx.lly.custom_view E/E:
colorChange 11-23 21:53:24.276 11194-11220/zzx.lly.custom_view E/E:
colorChange 11-23 21:53:24.286 11194-11220/zzx.lly.custom_view E/E:
colorChange 11-23 21:53:24.297 11194-11220/zzx.lly.custom_view E/E:
colorChange 11-23 21:53:24.303 11194-11219/zzx.lly.custom_view E/GED:
Failed to get GED Log Buf, err(0) 11-23 21:53:24.307
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.317
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.328
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.331
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.338
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.348
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.358
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.369
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.379
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.389
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.400
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.410
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.417
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.420
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.428
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.431
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.441
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.445
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.451
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.461
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.462
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.472
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.478
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.482
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.493
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.494
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.503
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.511
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.513
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.524
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.527
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.534
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.544
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.544
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.555
11194-11220/zzx.lly.custom_view E/E: colorChange 11-23 21:53:24.560
11194-11194/zzx.lly.custom_view E/E: draw 11-23 21:53:24.565
11194-11220/zzx.lly.custom_view E/E: colorChange
问题是什么?
我们知道onAttachToWindow(以下简称ATW)发生在view被添加到屏幕,这个过程在是onResume之后,draw之前,所以我们这里可以看到先被打印的是关于ATW的内容,ATW开启异步改变颜色的线程,问题在于我们看到本来应当是打印一次colorChange会发生一次invalidate,invalidate应当要调用ondraw,但是显然,这里在一开始的时候,出现了多次colorChange,说明在ATW之后相当长的一段时间内,ondraw都不能被调用.当然后面有出现一两个colorChange对应一个ondraw的情况,这是因为我们的子线程速度太快了,如果sleep时间稍微长一点就不会出现这种情况了.
尝试一下
colorEnd-=20; Log.e("E","colorChange"); if (colorEnd <= colorBegin/2) { colorEnd=colorBegin; } try { Thread.sleep(50); } catch (InterruptedException e) { e.printStackTrace(); }我们在这里将原本10毫秒休息一次改为50毫秒休息一次,然后再看日志,可以看到,现在一开始不响应的colorChange少了(这是因为子线程运行次数减少),并且一次colorChange一定有一次draw响应,符合预期.
11-23 22:06:23.717 12076-12076/zzx.lly.custom_view E/E: beforeOnAttach
AfterOnAttach 11-23 22:06:23.720 12076-12076/zzx.lly.custom_view E/E: onAttach 11-23 22:06:23.722 12076-12256/zzx.lly.custom_view E/E:
colorChange 11-23 22:06:23.774 12076-12256/zzx.lly.custom_view E/E:
colorChange 11-23 22:06:23.780 12076-12255/zzx.lly.custom_view E/GED:
Failed to get GED Log Buf, err(0) 11-23 22:06:23.824
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:23.839
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:23.877
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:23.928
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:23.978
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.009
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.028
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.033
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.049
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.079
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.096
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.129
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.146
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.180
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.195
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.230
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.245
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.281
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.294
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.331
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.344
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.381
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.393
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.432
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.442
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.482
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.492
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.532
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.541
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.583
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.591
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.633
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.641
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.685
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.691
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.736
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.740
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.788
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.789
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.840
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.855
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.892
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.904
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.944
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:24.954
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:24.994
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.004
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.046
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.053
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.097
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.111
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.148
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.152
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.201
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.202
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.253
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.268
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.305
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.317
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.356
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.367
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.409
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.416
12076-12076/zzx.lly.custom_view E/E: draw 11-23 22:06:25.466
12076-12256/zzx.lly.custom_view E/E: colorChange 11-23 22:06:25.482
12076-12076/zzx.lly.custom_view E/E: draw
总结
我们这里其实要实现这个效果不应当在ATW开启,而是应当在onDraw中进行一个判断,如果是第一次draw则开启子线程.另外使用Async也很麻烦,在实际中可以用rxjava代替
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