自定义视图的 OnDraw() 方法仅在单击按钮时调用一次
我试图在单击按钮时调用 onDraw 方法，按钮视图仅更新一次，并且 onDraw 方法也被调用。但线的位置没有变化。
我有这个自定义视图
public LineSeekbar(Context context) {
super(context);
this.setWillNotDraw(false);
setNewX(130);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Log.e("GRAPH","draw");
paint = new Paint();
paint.setARGB(225, 215, 10, 20);
paint.setStrokeWidth(2);
paint.setStyle(Style.FILL);
canvas.drawLine(130,900,getNewX(),100, paint);
setNewX(getNewX()+15);
}
从活动类调用它
final Bitmap mBackgroundImage = Bitmap.createBitmap(500,500, Bitmap.Config.RGB_565);
cv =new Canvas(mBackgroundImage);
LineView = new LineSeekbar(LineActivity.this);
LineView.setLayoutParams(new LayoutParams(500,500));
LineView.onMeasure(500,500);
LineView.invalidate();
LineView.draw(cv);
// LineView = null;
ImageView mImageView = new ImageView(this);
mImageView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
mImageView.setBackgroundColor(android.R.color.white);
mImageView.setImageBitmap( mBackgroundImage );
LinearLayout ll =(LinearLayout) findViewById(R.id.linearLayout1);
ll.addView(mImageView);
Button inc = (Button) findViewById(R.id.increase);
inc.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
LineView.invalidate();
LineView.draw(cv);
}
});
I'm trying to call onDraw method on Button click ,button the view is updated only once also onDraw method is called . But no change in the position of line.
I have this custom view
public LineSeekbar(Context context) {
super(context);
this.setWillNotDraw(false);
setNewX(130);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
Log.e("GRAPH","draw");
paint = new Paint();
paint.setARGB(225, 215, 10, 20);
paint.setStrokeWidth(2);
paint.setStyle(Style.FILL);
canvas.drawLine(130,900,getNewX(),100, paint);
setNewX(getNewX()+15);
}
Calling this from activity class
final Bitmap mBackgroundImage = Bitmap.createBitmap(500,500, Bitmap.Config.RGB_565);
cv =new Canvas(mBackgroundImage);
LineView = new LineSeekbar(LineActivity.this);
LineView.setLayoutParams(new LayoutParams(500,500));
LineView.onMeasure(500,500);
LineView.invalidate();
LineView.draw(cv);
// LineView = null;
ImageView mImageView = new ImageView(this);
mImageView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.FILL_PARENT));
mImageView.setBackgroundColor(android.R.color.white);
mImageView.setImageBitmap( mBackgroundImage );
LinearLayout ll =(LinearLayout) findViewById(R.id.linearLayout1);
ll.addView(mImageView);
Button inc = (Button) findViewById(R.id.increase);
inc.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
LineView.invalidate();
LineView.draw(cv);
}
});
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评论（3）
你应该用小写字母来调用一个实例，因为它不是一个类：lineView insted of LineView。
由于您是从另一个线程（UI）调用它，所以您应该说
当您第一次创建 LineView 实例时，onDraw 将自行执行并显示第一行。
目前还不清楚什么是 LineView.draw(cv);您可以在绘制线条之前在 onDraw 中绘制背景图像。您可以在自定义视图中使用 onSizeChange 方法来查找其实际尺寸并调整位图大小...
在 onDraw 中插入一条线
然后在 DDMS - LogCat 中观察按下按钮时的输出。
You should call an instance with small letter because it is not a class: lineView insted of LineView.
Since you are calling it from another thread (UI) you should say
When you create LineView instance for the first time, onDraw will be executed on its own and show the first line.
It is not clear what is LineView.draw(cv); You can draw the background image in onDraw just before drawing the line. You can use onSizeChange method in the custom view to find its real dimensions and resize your bitmap...
In onDraw insert a line
and then in DDMS - LogCat watch the output when you press the button.
试试这个：
您没有像您应该的那样创建 LineView 类的对象。例如，您应该使用小写字母。
Try this:
You didn't made an object of the LineView class like you should. You should use small letters for instances.
解决了，我将自定义视图放置在 xml 布局中，它工作正常。
Solved it ,I placed custom view in xml layout ,its working fine.