android 进阶自定义控件1

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}@Overrideprotected void onDraw(Canvas canvas) {// TODO Auto-generated method stubPaint 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：

 <com.example.kongjian_1.M_TextView        android:layout_width="200dp"        android:layout_height="50dp"        android:gravity="center"        android:text="android"        android:textColor="@android:color/black"        android:textSize="25sp" >    </com.example.kongjian_1.M_TextView>

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;@Overrideprotected 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();}}}@Overrideprotected 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：

<com.example.kongjian_1.M_TextView2        android:layout_width="200dp"        android:layout_height="50dp"        android:gravity="center"        android:text="android"        android:textColor="@android:color/black"        android:textSize="25sp" >    </com.example.kongjian_1.M_TextView2>

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