好久没有写博客了，趁着周末把Android自定义View这个知识点整理一下
Android自定义View主要有三种方式：
- 自绘控件
- 组合控件
- 继承控件
自绘控件
自绘控件所展现的内容都是绘制出来的。绘制的代码写在onDraw()方法中。如设计一个计时器：
public class CounterView extends View implements OnClickListener {
private Paint mPaint;
private Rect mBounds;
private int mCount;
public CounterView(Context context, AttributeSet attrs) {
super(context, attrs);
mPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mBounds = new Rect();
setOnClickListener(this);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
mPaint.setColor(Color.BLUE);
canvas.drawRect(0, 0, getWidth(), getHeight(), mPaint);
mPaint.setColor(Color.YELLOW);
mPaint.setTextSize(30);
String text = String.valueOf(mCount);
mPaint.getTextBounds(text, 0, text.length(), mBounds);
float textWidth = mBounds.width();
float textHeight = mBounds.height();
canvas.drawText(text, getWidth() / 2 - textWidth / 2, getHeight() / 2
+ textHeight / 2, mPaint);
}
@Override
public void onClick(View v) {
mCount++;
invalidate();
}
}
首先我们在CounterView的构造函数中初始化了数据并注册了点击事件，这样当CounterView被点击的时候，onClick()方法就会得到调用。而onClick()方法中对mCount这个计数器加1，然后调用invalidate()进行重绘，从而onDraw()被调用。
组合控件
组合控件就是可以将几个系统原生的控件组合到一起。标题栏是很常见的组合控件，下面就来尝试实现一个标题栏控件。
title.xml布局文件：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="50dp"
android:background="#ffcb05" >
<Button
android:id="@+id/button_left"
android:layout_width="60dp"
android:layout_height="40dp"
android:layout_centerVertical="true"
android:layout_marginLeft="5dp"
android:background="@drawable/back_button"
android:text="Back"
android:textColor="#fff" />
<TextView
android:id="@+id/title_text"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_centerInParent="true"
android:text="This is Title"
android:textColor="#fff"
android:textSize="20sp" />
</RelativeLayout>
TitleView类：
public class TitleView extends FrameLayout {
private Button leftButton;
private TextView titleText;
public TitleView(Context context, AttributeSet attrs) {
super(context, attrs);
LayoutInflater.from(context).inflate(R.layout.title, this);
titleText = (TextView) findViewById(R.id.title_text);
leftButton = (Button) findViewById(R.id.button_left);
leftButton.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
((Activity) getContext()).finish();
}
});
}
public void setTitleText(String text) {
titleText.setText(text);
}
public void setLeftButtonText(String text) {
leftButton.setText(text);
}
public void setLeftButtonListener(OnClickListener l) {
leftButton.setOnClickListener(l);
}
}
继承控件
继承控件就是继承现有的控件，然后在这个控件上增加一些新的功能，就可以形成一个自定义的控件了。
自定义attrs.xml属性文件：
<--圆形轮廓的宽度-->
<attr name="border_thickness" format="dimension"></attr>
<--圆形轮廓外边框的颜色-->
<attr name="border_outside_color" format="color"></attr>
<--圆形轮廓内边框的颜色-->
<attr name="border_inside_color" format="color"></attr>
RoundImageView类：
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.NinePatchDrawable;
import android.util.AttributeSet;
import android.util.Log;
import android.widget.ImageView;
public class RoundImageView extends ImageView {
private static final String TAG = "RoundImageView";
private static final boolean DEBUG = true;
private int mBorderThickness = 0;
private Context mContext;
private int defaultColor = 0xFFFFFFFF;
// 如果只有其中一个有值，则只画一个圆形边框
private int mBorderOutsideColor = 0;
private int mBorderInsideColor = 0;
// 控件默认长、宽
private int defaultWidth = 0;
private int defaultHeight = 0;
//控件画圆的宽高。
private int requestWH = 0;
public RoundImageView(Context context) {
this(context, null);
}
public RoundImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public RoundImageView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
mContext = context;
setCustomAttributes(attrs);
}
/**
* 获得自定义控件属性值
*
* @param attrs
*/
private void setCustomAttributes(AttributeSet attrs) {
TypedArray a = mContext.obtainStyledAttributes(attrs,
R.styleable.RoundImageView);
mBorderThickness = a.getDimensionPixelSize(
R.styleable.RoundImageView_border_thickness, 0);
mBorderOutsideColor = a
.getColor(R.styleable.RoundImageView_border_outside_color,
defaultColor);
mBorderInsideColor = a.getColor(
R.styleable.RoundImageView_border_inside_color, defaultColor);
a.recycle();
}
@Override
protected void onDraw(Canvas canvas) {
Drawable drawable = getDrawable();
if (drawable == null) {
return;
}
if (getWidth() == 0 || getHeight() == 0) {
return;
}
this.measure(0, 0);
if (drawable.getClass() == NinePatchDrawable.class) {
return;
}
Bitmap b = ((BitmapDrawable) drawable).getBitmap();
Bitmap bitmap = b.copy(Bitmap.Config.ARGB_8888, true);
int radius = getRadius(canvas);
Bitmap roundBitmap = getCroppedRoundBitmap(bitmap, radius);
canvas.drawBitmap(roundBitmap, requestWH / 2 - radius, requestWH
/ 2 - radius, null);
}
/**
* 获取画园的半径，并且绘制圆的外边框
*
* @param canvas
* @return
*/
private int getRadius(Canvas canvas) {
if (defaultWidth == 0) {
defaultWidth = getWidth();
}
if (defaultHeight == 0) {
defaultHeight = getHeight();
}
requestWH = defaultHeight > defaultWidth ? defaultWidth : defaultHeight;
int radius = 0;
if (mBorderInsideColor != defaultColor
&& mBorderOutsideColor != defaultColor) {// 定义画两个边框，分别为外圆边框和内圆边框
radius = requestWH / 2 - 2 * mBorderThickness;
// 画内圆
drawCircleBorder(canvas, radius + mBorderThickness / 2,
mBorderInsideColor);
// 画外圆
drawCircleBorder(canvas, radius + mBorderThickness
+ mBorderThickness / 2, mBorderOutsideColor);
} else if (mBorderInsideColor != defaultColor
&& mBorderOutsideColor == defaultColor) {// 定义画一个边框
radius = requestWH / 2 - mBorderThickness;
drawCircleBorder(canvas, radius + mBorderThickness / 2,
mBorderInsideColor);
} else if (mBorderInsideColor == defaultColor
&& mBorderOutsideColor != defaultColor) {// 定义画一个边框
radius = (defaultWidth < defaultHeight ? defaultWidth
: defaultHeight) / 2 - mBorderThickness;
drawCircleBorder(canvas, radius + mBorderThickness / 2,
mBorderOutsideColor);
} else {// 没有边框
radius = requestWH / 2;
}
return radius;
}
/**
* 获取裁剪后的圆形图片
*
* @param radius 半径
*/
private static Bitmap getCroppedRoundBitmap(Bitmap bmp, int radius) {
Bitmap scaledSrcBmp;
int diameter = radius * 2;
// 为了防止宽高不相等，造成圆形图片变形，因此截取长方形中处于中间位置最大的正方形图片
int bmpWidth = bmp.getWidth();
int bmpHeight = bmp.getHeight();
int squareWidth = 0, squareHeight = 0;
int x = 0, y = 0;
Bitmap squareBitmap;
if (DEBUG) {
Log.d(TAG, "the Bitmap w:" + bmpWidth + " the Bitmap h:" + bmpHeight);
}
if (bmpHeight > bmpWidth) {// 高大于宽
squareWidth = squareHeight = bmpWidth;
x = 0;
y = (bmpHeight - bmpWidth) / 2;
// 截取正方形图片
squareBitmap = Bitmap.createBitmap(bmp, x, y, squareWidth,
squareHeight);
} else if (bmpHeight < bmpWidth) {// 宽大于高
squareWidth = squareHeight = bmpHeight;
x = (bmpWidth - bmpHeight) / 2;
y = 0;
squareBitmap = Bitmap.createBitmap(bmp, x, y, squareWidth,
squareHeight);
} else {
squareBitmap = bmp;
}
if (squareBitmap.getWidth() != diameter
|| squareBitmap.getHeight() != diameter) {
scaledSrcBmp = Bitmap.createScaledBitmap(squareBitmap, diameter,
diameter, true);
} else {
scaledSrcBmp = squareBitmap;
}
Bitmap output = Bitmap.createBitmap(scaledSrcBmp.getWidth(),
scaledSrcBmp.getHeight(), Bitmap.Config.ARGB_8888);
Canvas canvas = new Canvas(output);
Paint paint = new Paint();
Rect rect = new Rect(0, 0, scaledSrcBmp.getWidth(),
scaledSrcBmp.getHeight());
paint.setAntiAlias(true);
paint.setFilterBitmap(true);
paint.setDither(true);
canvas.drawARGB(0, 0, 0, 0);
canvas.drawCircle(scaledSrcBmp.getWidth() / 2,
scaledSrcBmp.getHeight() / 2, scaledSrcBmp.getWidth() / 2,
paint);
paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.SRC_IN));
canvas.drawBitmap(scaledSrcBmp, rect, rect, paint);
bmp.recycle();
squareBitmap.recycle();
scaledSrcBmp.recycle();
bmp = null;
squareBitmap = null;
scaledSrcBmp = null;
return output;
}
/**
* 边缘画圆
*/
private void drawCircleBorder(Canvas canvas, int radius, int color) {
Paint paint = new Paint();
/* 去锯齿 */
paint.setAntiAlias(true);
paint.setFilterBitmap(true);
paint.setDither(true);
paint.setColor(color);
/* 设置paint的 style 为STROKE：空心 */
paint.setStyle(Paint.Style.STROKE);
/* 设置paint的外框宽度 */
paint.setStrokeWidth(mBorderThickness);
canvas.drawCircle(requestWH / 2, requestWH / 2, radius, paint);
}
/**
* 设置外边框的宽度
*
* @param borderWith
*/
public void setBorderWith(int borderWith) {
mBorderThickness = borderWith;
}
/**
* 设置外边框的颜色
*
* @param outsideColor
*/
public void setBorderOutsideColor(int outsideColor) {
mBorderOutsideColor = outsideColor;
}
/**
* 设置内边框的颜色
*
* @param insideColor
*/
public void setBorderInsideColor(int insideColor) {
mBorderInsideColor = insideColor;
}
}