Question

我试图在Android中掌握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

我已经通过扩展Android drawable来定义一个自定义的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;
   }
 }

我想在我的活动中显示这个，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);

    }
}

但是当我运行应用程序时，我看到活动上没有矩形，有人可以帮助我吗？我哪里错了？

Answer 1

您的问题出在getOpacity()方法中。 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RectF和Paint，然后只调整draw()中的值，这样就不会创建那么多需要垃圾回收的对象。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)
    {
    }
}

Answer 2

您可能必须实现其他覆盖，例如getIntrinsicWidth（）和getIntrinsicHeight（）。一种方法是将layout_width和layout_height设置为某个常量（layout_width =＆＃34; 42dip＆＃34; layout_height =＆＃34; 42dip＆＃34;在XML中或如果您使用Java将layoutParams设置为某个值布局）。有些View类型处理没有getIntrinsic *实现，所以试试吧！这包括直观视图

如果没有特定的宽度或高度，您可以尝试返回-1。

很难说这个问题是否得到了解决，但我是通过Google来到这里试图帮助自己记住制作自定义Drawable的细节，而且我想帮助人们避免这个问题：http://xkcd.com/979/

在Android中实现自定义drawable

2 个答案: