经过上一篇的介绍，大家对于自定义View一定有了一定的认识，接下来我们就以实现一个图片下显示文字的自定义View来练习一下。废话不多说，下面进入我们的正题，首先看一下我们的思路，1、我们需要通过在values文件夹下添加一个attrs的文件，里面设置我们的自定义属性；2、通过重写View类，来获得我们设置的自定义属性的参数，并进行绘制；3、在我们的视图文件中进行引用。好了到这里我们的基本思路就已经形成，下面我们开始进行我们的实战编码操作。
第一步：在res目录下，values文件夹下，新建一个attrs.xml文件：
<?xml version="1.0" encoding="utf-8"?>
<resources> <attr name="TitleText" format="string" />
<attr name="TitleColor" format="color" />
<attr name="TitleSize" format="dimension" /> <attr name="image" format="reference" />
<attr name="imageScaleType">
<enum name="fillXY" value="" />
<enum name="center" value="" />
</attr> <declare-styleable name="CustomImageView">
<attr name="TitleText" />
<attr name="TitleColor" />
<attr name="TitleSize" />
<attr name="image" />
<attr name="imageScaleType" />
</declare-styleable> </resources>
提示一下：format对应的是该参数的值类型
第二步：重写我们的View类：
public class MySelfImageView extends View {
/*
* 图片区域
*/
Rect imageRect;
/*
* 文字区域
*/
Rect titleRect;
/*
* 画笔对象
*/
Paint mPaint;
/*
* 图片标题文字
*/
String titleText;
/*
* 图片标题文字颜色
*/
int titleColor;
/*
* 图片标题文字大小
*/
int titleSize;
/*
* 图片资源
*/
Bitmap image;
/*
* 图片资源显示样式
*/
int imageFillXY;
int mWidth = 0;
int mHeight = 0;
public MySelfImageView(Context context) {
this(context, null);
}
public MySelfImageView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public MySelfImageView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
//获取自定义设置的属性
TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyleAttr, 0);
int n = typedArray.getIndexCount();
for(int i=0; i<n; i++){
int att = typedArray.getIndex(i);
//分别取出自定义属性设置的值
switch (att) {
case R.styleable.CustomImageView_TitleText:
titleText = typedArray.getString(att);
break;
case R.styleable.CustomImageView_TitleColor:
titleColor = typedArray.getColor(att, Color.RED);
break;
case R.styleable.CustomImageView_TitleSize:
titleSize = typedArray.getDimensionPixelSize(att, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,
16, getResources().getDisplayMetrics()));
break;
case R.styleable.CustomImageView_image:
image = BitmapFactory.decodeResource(getResources(), typedArray.getResourceId(att, 0));
break;
case R.styleable.CustomImageView_imageScaleType:
imageFillXY = typedArray.getInt(att, 0);
break;
}
}
typedArray.recycle();
imageRect = new Rect();
mPaint = new Paint();
titleRect = new Rect();
mPaint.setTextSize(titleSize);
// 计算描绘字体需要的范围
mPaint.getTextBounds(titleText, 0, titleText.length(), titleRect);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
/**
* 设置宽度
*/
int specMode = MeasureSpec.getMode(widthMeasureSpec);
int specSize = MeasureSpec.getSize(widthMeasureSpec);
if(specMode == MeasureSpec.EXACTLY){
mWidth = specSize;
}else{
// 由图片决定的宽
int desireByImg = getPaddingLeft() + getPaddingRight() + image.getWidth();
// 由字体决定的宽
int desireByTitle = getPaddingLeft() + getPaddingRight() + titleRect.width();
if (specMode == MeasureSpec.AT_MOST){// wrap_content
int desire = Math.max(desireByImg, desireByTitle);
mWidth = Math.min(desire, specSize);
}
}
/**
* 设置高度
*/
specMode = MeasureSpec.getMode(heightMeasureSpec);
specSize = MeasureSpec.getSize(heightMeasureSpec);
if(specMode == MeasureSpec.EXACTLY){
mHeight = specSize;
}else{
int desire = getPaddingTop() + getPaddingBottom() + image.getHeight() + titleRect.height();
if (specMode == MeasureSpec.AT_MOST){// wrap_content
mHeight = Math.min(desire, specSize);
}
}
setMeasuredDimension(mWidth, mHeight);
}
@Override
protected void onDraw(Canvas canvas) {
/**
* 边框
*/
mPaint.setStrokeWidth(4);//设置空心线宽
mPaint.setStyle(Paint.Style.STROKE);//设置画笔为空心
mPaint.setColor(Color.CYAN);//设置画笔颜色
canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);
imageRect.left = getPaddingLeft();
imageRect.right = mWidth - getPaddingRight();
imageRect.top = getPaddingTop();
imageRect.bottom = mHeight - getPaddingBottom();
mPaint.setColor(titleColor);
mPaint.setStyle(Style.FILL);
/**
* 当前设置的宽度小于字体需要的宽度，将字体改为xxx...
*/
if (titleRect.width() > mWidth) {
TextPaint paint = new TextPaint(mPaint);
String msg = TextUtils.ellipsize(titleText, paint, (float) mWidth - getPaddingLeft() - getPaddingRight(),
TextUtils.TruncateAt.END).toString();
canvas.drawText(msg, getPaddingLeft(), mHeight - getPaddingBottom(), mPaint);
} else {
//正常情况，将字体居中
canvas.drawText(titleText, mWidth / 2 - titleRect.width() * 1.0f / 2, mHeight - getPaddingBottom(), mPaint);
}
//取消使用掉的块
imageRect.bottom -= titleRect.height();
if (imageFillXY == 0) {
canvas.drawBitmap(image, null, imageRect, mPaint);
} else {
//计算居中的矩形范围
imageRect.left = mWidth / 2 - image.getWidth() / 2;
imageRect.right = mWidth / 2 + image.getWidth() / 2;
imageRect.top = (mHeight - titleRect.height()) / 2 - image.getHeight() / 2;
imageRect.bottom = (mHeight - titleRect.height()) / 2 + image.getHeight() / 2;
canvas.drawBitmap(image, null, imageRect, mPaint);
}
}
}
第三步：布局文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:zhy="http://schemas.android.com/apk/res/com.example.myselfview"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" > <com.example.myselfview.view.MySelfImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:padding="10dp"
zhy:image="@drawable/ic_launcher"
zhy:imageScaleType="center"
zhy:TitleText="hello andorid ! "
zhy:TitleColor="#ff0000"
zhy:TitleSize="30sp" /> <com.example.myselfview.view.MySelfImageView
android:layout_width="100dp"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:padding="10dp"
zhy:image="@drawable/ic_launcher"
zhy:imageScaleType="center"
zhy:TitleText="helloworldwelcome"
zhy:TitleColor="#00ff00"
zhy:TitleSize="20sp" /> <com.example.myselfview.view.MySelfImageView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_margin="10dp"
android:padding="10dp"
zhy:image="@drawable/im"
zhy:imageScaleType="center"
zhy:TitleText="山水美景"
zhy:TitleColor="#ff0000"
zhy:TitleSize="12sp" /> </LinearLayout>
最后效果图：
相对第一、三步，第二步相对更复杂一些，下面我就对第二步里面的具体内容进行一下解析：
//获取自定义设置的属性
TypedArray typedArray = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomImageView, defStyleAttr, 0);
int n = typedArray.getIndexCount();
for(int i=0; i<n; i++){
int att = typedArray.getIndex(i);
//分别取出自定义属性设置的值
switch (att) {
case R.styleable.CustomImageView_TitleText:
titleText = typedArray.getString(att);
break;
case R.styleable.CustomImageView_TitleColor:
titleColor = typedArray.getColor(att, Color.RED);
break;
case R.styleable.CustomImageView_TitleSize:
titleSize = typedArray.getDimensionPixelSize(att, (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_SP,
16, getResources().getDisplayMetrics()));
break;
case R.styleable.CustomImageView_image:
image = BitmapFactory.decodeResource(getResources(), typedArray.getResourceId(att, 0));
break;
case R.styleable.CustomImageView_imageScaleType:
imageFillXY = typedArray.getInt(att, 0);
break;
}
}
typedArray.recycle();
作用是获取我们在attrs中设置的自定义参数，在布局文件中进行的赋值。
onMeasure()方法用于设置控件的宽度，控件的长宽值如何取得呢？下面我们就来进行一下解析：
最后是我们绘图方法onDraw(Canvas canvas):
@Override
protected void onDraw(Canvas canvas) {
/**
* 空心矩形绘制
*/
mPaint.setStrokeWidth(4);//设置空心线宽
mPaint.setStyle(Paint.Style.STROKE);//设置画笔为空心
mPaint.setColor(Color.CYAN);//设置画笔颜色
canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint); imageRect.left = getPaddingLeft();//获取图片左上角坐标
imageRect.right = mWidth - getPaddingRight();//获取图片右上角坐标
imageRect.top = getPaddingTop();//获取图片距控件顶部距离
imageRect.bottom = mHeight - getPaddingBottom();//确定图片底部坐标 mPaint.setColor(titleColor);//设置文本的颜色
mPaint.setStyle(Style.FILL);//设置文本内容的填充方式
/**
* 当前设置的宽度小于字体需要的宽度，将字体改为xxx...
*/
if (titleRect.width() > mWidth) {
TextPaint paint = new TextPaint(mPaint);
String msg = TextUtils.ellipsize(titleText, paint, (float) mWidth - getPaddingLeft() - getPaddingRight(),
TextUtils.TruncateAt.END).toString();
canvas.drawText(msg, getPaddingLeft(), mHeight - getPaddingBottom(), mPaint);
} else {
//正常情况，将字体居中
canvas.drawText(titleText, mWidth / 2 - titleRect.width() * 1.0f / 2, mHeight - getPaddingBottom(), mPaint);
} //取消使用掉的块
imageRect.bottom -= titleRect.height();//因为文字内容占用一定的高度，所以图片的底部坐标需要上移。 if (imageFillXY == 0) {
canvas.drawBitmap(image, null, imageRect, mPaint);
} else {
//计算居中的矩形范围
imageRect.left = mWidth / 2 - image.getWidth() / 2;
imageRect.right = mWidth / 2 + image.getWidth() / 2;
imageRect.top = (mHeight - titleRect.height()) / 2 - image.getHeight() / 2;
imageRect.bottom = (mHeight - titleRect.height()) / 2 + image.getHeight() / 2; canvas.drawBitmap(image, null, imageRect, mPaint);
}
}
好了，到这里关于自定义View的初步学习就介绍完毕，如果你有更好的关于自定义View的文章，欢迎留言交流。