Android 创建自定义 ImageView
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Creating Custom ImageView
提问by Prabhu R
I create a custom image view by extending ImageView that just draws some text on the screen, however I don't see anything painted in the Emulator Screen, but the log messages and the printlns get printed in the log console. Am I not doing something?
我通过扩展 ImageView 创建了一个自定义图像视图，它只是在屏幕上绘制一些文本，但是我在模拟器屏幕中没有看到任何绘制的内容，但是日志消息和 println 会在日志控制台中打印出来。我不是在做什么吗？
This is my activity
这是我的活动
public class HelloAndroidActivity extends Activity
{
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
// setContentView(R.layout.main);
CustomImageView myView = new CustomImageView(getApplicationContext());
System.out.println("Setting the view");
myView.invalidate();
setContentView(myView);
System.out.println("Calling invalidate");
}
}
This is my CustomImageView
这是我的 CustomImageView
public class CustomImageView extends ImageView
{
/**
* @param context
*/
public CustomImageView(Context context)
{
super(context);
// TODO Auto-generated constructor stub
setBackgroundColor(0xFFFFFF);
}
/**
* @param context
* @param attrs
*/
public CustomImageView(Context context, AttributeSet attrs)
{
super(context, attrs);
// TODO Auto-generated constructor stub
}
/**
* @param context
* @param attrs
* @param defStyle
*/
public CustomImageView(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
}
@Override
protected void onDraw(Canvas canvas)
{
// TODO Auto-generated method stub
super.onDraw(canvas);
System.out.println("Painting content");
Paint paint = new Paint(Paint.LINEAR_TEXT_FLAG);
paint.setColor(0x0);
paint.setTextSize(12.0F);
System.out.println("Drawing text");
canvas.drawText("Hello World in custom view", 100, 100, paint);
}
@Override
public boolean onTouchEvent(MotionEvent event)
{
// TODO Auto-generated method stub
Log.d("Hello Android", "Got a touch event: " + event.getAction());
return super.onTouchEvent(event);
}
}
Even the log message in the onTouchEvent() gets printed, but nothing is painted.
甚至 onTouchEvent() 中的日志消息也被打印出来，但没有绘制任何内容。
This is my main.xml that has the layout
这是我的具有布局的 main.xml
<?xml version="1.0" encoding="utf-8"?>
<AbsoluteLayout android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/AbsoluteLayout">
</AbsoluteLayout>
采纳答案by bhatt4982
Use color values Color.WHITEor Color.BLACKinstead of hexa values.
使用颜色值Color.WHITE或Color.BLACK而不是十六进制值。
回答by JavaCoderEx
Have you checked your canvas size? An image view expects the bitmap/drawable to return its size and based on the scaletype flags, determine the size of the view. I don't see anything in your code that determines the size of the view for layout needs.
你检查过你的画布尺寸吗？图像视图期望位图/可绘制对象返回其大小，并根据 scaletype 标志确定视图的大小。我在您的代码中看不到任何决定布局需求的视图大小的内容。
-Rick
-瑞克
