android中的控件继承自,android 自定义控件继承TextView

在原生控件上进行扩展，增加新的功能

一般是在onDraw() 方法中对原生控件进行扩展

下面以一个TextView 为例，来看看如何使用扩展原生控件的方法创建新的控件

/*

* 对现有控件进行扩展

* */

public class M_TextView extends TextView{

public M_TextView(Context context, AttributeSet attrs, int defStyle) {

super(context, attrs, defStyle);

// TODO Auto-generated constructor stub

}

public M_TextView(Context context, AttributeSet attrs) {

super(context, attrs);

// TODO Auto-generated constructor stub

}

public M_TextView(Context context) {

super(context);

// TODO Auto-generated constructor stub

}

@Override

protected void onDraw(Canvas canvas) {

// TODO Auto-generated method stub

Paint mPaint1 = new Paint();

mPaint1.setColor(getResources().getColor(android.R.color.holo_blue_light));

mPaint1.setStyle(Paint.Style.FILL);

Paint mPaint2 = new Paint();

mPaint2.setColor(Color.YELLOW);

mPaint2.setStyle(Paint.Style.FILL);

//绘制外层矩形

canvas.drawRect(0, 0, getMeasuredWidth(),getMeasuredHeight(), mPaint1);

//绘制内层矩形

canvas.drawRect(10, 10, getMeasuredWidth()-10, getMeasuredHeight()-10, mPaint2);

canvas.save();

//绘制文字前平移10像素

canvas.translate(10, 0);

super.onDraw(canvas);

canvas.restore();

}

}在布局文件中使用：

实例二：给文字增加闪动效果：

public class M_TextView2 extends TextView {

public M_TextView2(Context context) {

super(context);

// TODO Auto-generated constructor stub

}

public M_TextView2(Context context, AttributeSet attrs, int defStyle) {

super(context, attrs, defStyle);

// TODO Auto-generated constructor stub

}

public M_TextView2(Context context, AttributeSet attrs) {

super(context, attrs);

// TODO Auto-generated constructor stub

}

private LinearGradient mLinearGradient;

private Matrix mGradientMatrix;

private Paint mPaint;

private int mViewWidth = 0;

private int mTranslate = 0;

@Override

protected void onSizeChanged(int w, int h, int oldw, int oldh) {

super.onSizeChanged(w, h, oldw, oldh);

if (mViewWidth == 0) {

mViewWidth = getMeasuredWidth();

if (mViewWidth > 0) {

mPaint = getPaint();

mLinearGradient = new LinearGradient(

0,

0,

mViewWidth,

0,

new int[]{

Color.BLUE, 0xffffffff,

Color.BLUE},

null,

Shader.TileMode.CLAMP);

mPaint.setShader(mLinearGradient);

mGradientMatrix = new Matrix();

}

}

}

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

if (mGradientMatrix != null) {

mTranslate += mViewWidth / 5;

if (mTranslate > 2 * mViewWidth) {

mTranslate = -mViewWidth;

}

mGradientMatrix.setTranslate(mTranslate, 0);

mLinearGradient.setLocalMatrix(mGradientMatrix);

postInvalidateDelayed(50);

}

}

}

xml中使用：