Android EditText搜索框实现图标居中

package mobi.truekey.weapp2.widget;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Paint;import android.graphics.drawable.Drawable;import android.util.AttributeSet;import android.widget.EditText;import mobi.truekey.weapp2.R;public class SearchView extends EditText {  private float searchSize = 0;  private float textSize = 0;  private int textColor = 0xFF000000;  private Drawable mDrawable;  private Paint paint;  public SearchView(Context context, AttributeSet attrs) {    super(context, attrs);    InitResource(context, attrs);    InitPaint();  }  private void InitResource(Context context, AttributeSet attrs) {    TypedArray mTypedArray = context.obtainStyledAttributes(attrs, R.styleable.searchedit);    float density = context.getResources().getDisplayMetrics().density;    searchSize = mTypedArray.getDimension(R.styleable.searchedit_imagewidth, 18 * density + 0.5F);    textColor = mTypedArray.getColor(R.styleable.searchedit_textColor, 0xFF848484);    textSize = mTypedArray.getDimension(R.styleable.searchedit_textSize, 14 * density + 0.5F);    mTypedArray.recycle();  }  private void InitPaint() {    paint = new Paint(Paint.ANTI_ALIAS_FLAG);    paint.setColor(textColor);    paint.setTextSize(textSize);  }  @Override  protected void onDraw(Canvas canvas) {    super.onDraw(canvas);    DrawSearchIcon(canvas);  }  private void DrawSearchIcon(Canvas canvas) {    if (this.getText().toString().length() == 0) {      float textWidth = paint.measureText("搜索");      float textHeight = getFontLeading(paint);      float dx = (getWidth() - searchSize - textWidth - 8) / 2;      float dy = (getHeight() - searchSize) / 2;      canvas.save();      canvas.translate(getScrollX() + dx, getScrollY() + dy);      if (mDrawable != null) {        mDrawable.draw(canvas);      }      canvas.drawText("搜索", getScrollX() + searchSize + 8, getScrollY() + (getHeight() - (getHeight() - textHeight) / 2) - paint.getFontMetrics().bottom - dy, paint);      canvas.restore();    }  }  @Override  protected void onAttachedToWindow() {    super.onAttachedToWindow();    if (mDrawable == null) {      try {        mDrawable = getContext().getResources().getDrawable(R.drawable.search);        mDrawable.setBounds(0, 0, (int) searchSize, (int) searchSize);      } catch (Exception e) {      }    }  }  @Override  protected void onDetachedFromWindow() {    if (mDrawable != null) {      mDrawable.setCallback(null);      mDrawable = null;    }    super.onDetachedFromWindow();  }  public float getFontLeading(Paint paint) {    Paint.FontMetrics fm = paint.getFontMetrics();    return fm.bottom - fm.top;  }}