在 Android 中实现自定义 drawable
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Implementing a customized drawable in Android
提问by Girish
I was trying to get hold of 2D graphics in Android. As a example i want to implement a custom drawable and show it in my Activity
我试图在 Android 中获取 2D 图形。作为一个例子，我想实现一个自定义 drawable 并在我的 Activity 中显示它
I have defined a customized drawable by extending from Android drawable as mentioned below
我通过从 Android drawable 扩展定义了一个自定义的 drawable，如下所述
class myDrawable extends Drawable {
private static final String TAG = myDrawable.class.getSimpleName();
private ColorFilter cf;
@Override
public void draw(Canvas canvas) {
//First you define a colour for the outline of your rectangle
Paint rectanglePaint = new Paint();
rectanglePaint.setARGB(255, 255, 0, 0);
rectanglePaint.setStrokeWidth(2);
rectanglePaint.setStyle(Style.FILL);
//Then create yourself a Rectangle
RectF rectangle = new RectF(15.0f, 50.0f, 55.0f, 75.0f); //in pixels
Log.d(TAG,"On Draw method");
// TODO Auto-generated method stub
Paint paintHandl = new Paint();
// paintHandl.setColor(0xaabbcc);
paintHandl.setARGB(125, 234, 213, 34 );
RectF rectObj = new RectF(5,5,25,25);
canvas.drawRoundRect(rectangle, 0.5f, 0.5f, rectanglePaint);
}
@Override
public int getOpacity() {
// TODO Auto-generated method stub
return 100;
}
@Override
public void setAlpha(int alpha) {
// TODO Auto-generated method stub
}
@Override
public void setColorFilter(ColorFilter cf) {
// TODO Auto-generated method stub
this.cf = cf;
}
}
I am trying to get this displayed in my activity, as shown below
我正在尝试将其显示在我的活动中，如下所示
public class custDrawable extends Activity {
/** Called when the activity is first created. */
LinearLayout layObj = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
layObj = (LinearLayout) findViewById(R.id.parentLay);
ImageView imageView = (ImageView) findViewById(R.id.icon2);
myDrawable myDrawObj = new myDrawable();
imageView.setImageDrawable(myDrawObj);
imageView.invalidate();
// layObj.addView(myDrawObj, params);
}
}
But when i run the app i see no rectangle on the activity, can anyone help me out? Where am i going wrong?
但是当我运行应用程序时，我在活动中看不到矩形，有人可以帮我吗？我哪里出错了？
回答by CaseyB
Your problem is in the getOpacity()method. 100 is not a valid value. You should use a PixelFormatvalue. Also, you should create your RectFand Paintin the constructor and then just adjust the values in draw()so you don't create so many objects that need garbage collected. Like this:
你的问题出在getOpacity()方法上。100 不是有效值。您应该使用PixelFormat值。此外，您应该在构造函数中创建您的RectF和Paint，然后调整其中的值，draw()这样您就不会创建太多需要垃圾收集的对象。像这样：
public class Square extends Drawable
{
private final Paint mPaint;
private final RectF mRect;
public Square()
{
mPaint = new Paint();
mRect = new RectF();
}
@Override
public void draw(Canvas canvas)
{
// Set the correct values in the Paint
mPaint.setARGB(255, 255, 0, 0);
mPaint.setStrokeWidth(2);
mPaint.setStyle(Style.FILL);
// Adjust the rect
mRect.left = 15.0f;
mRect.top = 50.0f;
mRect.right = 55.0f;
mRect.bottom = 75.0f;
// Draw it
canvas.drawRoundRect(mRect, 0.5f, 0.5f, mPaint);
}
@Override
public int getOpacity()
{
return PixelFormat.OPAQUE;
}
@Override
public void setAlpha(int arg0)
{
}
@Override
public void setColorFilter(ColorFilter arg0)
{
}
}
回答by Joe Plante
You may have to implement other overrides like getIntrinsicWidthand getIntrinsicHeight. One way to tell is that you set your layout_width and layout_heightto some constant (layout_width="42dip"layout_height="42dip"in XML or setting your layoutParamsto some value if you are using Java layouts). Some Viewtypes handle not having getIntrinsic*implemented than others, so try them! This includes a straight View.
您可能需要实现其他覆盖，例如getIntrinsicWidth和getIntrinsicHeight。一种判断方法是将 layout_width 设置layout_height为某个常量（layout_width="42dip"layout_height="42dip"在 XML 中，或者layoutParams如果使用 Java 布局，则将其设置为某个值）。有些View类型处理没有getIntrinsic*实现比其他类型，所以尝试它们！这包括一个直线View。
You can try returning -1 if there's no specific width or height.
如果没有特定的宽度或高度，您可以尝试返回 -1。
Hard to tell if the issue ever got resolved, but I got here via Google trying to help myself remember the details of making a custom Drawable, plus I want to help people avoid this: http://xkcd.com/979/
很难说问题是否得到解决，但我通过谷歌来到这里，试图帮助自己记住定制的细节Drawable，另外我想帮助人们避免这种情况：http: //xkcd.com/979/
