android自定义view学习笔记1

1、android自定义View属性，需要在res/values/下建立一个attrs.xml，在里面声明需要自定义的属性。

<?xml version="1.0" encoding="utf-8"?><resources>    <attr name="titleText" format="string"/>    <attr name="titleTextColor2" format="color"/>    <attr name="titleTextSize" format="dimension"/>    <declare-styleable name="CustomTitleView">        <attr name="titleText"/>        <attr name="titleTextColor2"/>        <attr name="titleTextSize"/>    </declare-styleable></resources>

这里自定义字体、字体大小、字体颜色三个属性，format是属性的取值类型，一共有：string,color,dimension,interger,enum,reference,float,boolean,fraction,flag，这几种类型。
2、自定义View样式：

package com.example.myapplication;import android.content.Context;import android.content.res.TypedArray;import android.graphics.Canvas;import android.graphics.Color;import android.graphics.Paint;import android.graphics.Rect;import android.util.AttributeSet;import android.util.Log;import android.view.View;import java.util.HashSet;import java.util.Random;import java.util.Set;/** * Created by Administrator on 2016/7/30. */public class CustomTitleView extends View {    private String mTitleText;    private int mTitleTextColor;    private int mTitleTextSize;    private Rect mBound;    private Paint mPaint;    public CustomTitleView(Context context) {        this(context, null);    }    public CustomTitleView(Context context, AttributeSet attrs) {        this(context, attrs, 0);    }    public CustomTitleView(Context context, AttributeSet attrs, int defStyleAttr) {        super(context, attrs, defStyleAttr);        TypedArray a = context.getTheme().obtainStyledAttributes(attrs, R.styleable.CustomTitleView, defStyleAttr, 0);        int n = a.getIndexCount();        for (int i = 0; i < n; i++) {            int attr = a.getIndex(i);            switch (attr) {                case R.styleable.CustomTitleView_titleText:                    mTitleText = a.getString(attr);                    break;                case R.styleable.CustomTitleView_titleTextColor2:                    mTitleTextColor = a.getColor(attr, Color.BLACK);                    break;                case R.styleable.CustomTitleView_titleTextSize:                    mTitleTextSize = a.getDimensionPixelSize(attr, 20);                    break;            }        }        a.recycle();        mPaint = new Paint();        mPaint.setTextSize(mTitleTextSize);        mBound = new Rect();        mPaint.getTextBounds(mTitleText, 0, mTitleText.length(), mBound);        this.setOnClickListener(new OnClickListener() {            @Override            public void onClick(View view) {                mTitleText = randomText();                postInvalidate();            }        });    }    private String randomText() {        Random random = new Random();        Set<Integer> set = new HashSet<Integer>();        Log.d("=====[CustomTitleView]:", "   set.size()=" + set.size());        while (set.size() < 4) {            int randomInt = random.nextInt(10);            set.add(randomInt);        }        StringBuffer sb = new StringBuffer();        for (Integer i : set) {            sb.append("" + i);        }        return sb.toString();    }    @Override    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {        //super.onMeasure(widthMeasureSpec, heightMeasureSpec);        int width = 0;        int height = 0;      /*MeasureSpec的specMode一共三种类型：        EXACTLY：一般是设置了明确的值或者是MATCH_PARENT        AT_MOST：表示子布局限制在一个最大值内，一般为WARP_CONTENT        UNSPECIFIED：表示子布局想要多大就多大，很少使用*/        int specMode = MeasureSpec.getMode(widthMeasureSpec);        int specSize = MeasureSpec.getSize(widthMeasureSpec);        switch (specMode) {            case MeasureSpec.EXACTLY:                width = getPaddingLeft() + getPaddingRight() + specSize;                break;            case MeasureSpec.AT_MOST:                width = getPaddingLeft() + getPaddingRight() + mBound.width();                break;        }        specMode = MeasureSpec.getMode(heightMeasureSpec);        specSize = MeasureSpec.getSize(heightMeasureSpec);        switch (specMode) {            case MeasureSpec.EXACTLY:                height = getPaddingBottom() + getPaddingTop() + specSize;                break;            case MeasureSpec.AT_MOST:                height = getPaddingBottom() + getPaddingTop() + mBound.height();                break;        }        setMeasuredDimension(width, height);    }    @Override    protected void onDraw(Canvas canvas) {        //super.onDraw(canvas);        mPaint.setColor(Color.YELLOW);        canvas.drawRect(0, 0, getMeasuredWidth(), getMeasuredHeight(), mPaint);        mPaint.setColor(mTitleTextColor);        canvas.drawText(mTitleText, getWidth() / 2 - mBound.width() / 2, getHeight() / 2 + mBound.height() / 2, mPaint);    }}

主要是在构造方法中获取自定义属性，然后重写onMeasure和onDraw两个方法。
3、在布局文件中引用自定义View

<?xml version="1.0" encoding="utf-8"?><RelativeLayout    xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    xmlns:custom="http://schemas.android.com/apk/res/com.example.myapplication"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.example.myapplication.MainActivity">    <com.example.myapplication.CustomTitleView        android:layout_width="200dp"        android:layout_height="100dp"        custom:titleText="3712"        android:padding="10dp"        custom:titleTextColor2="#ff0000"        custom:titleTextSize="40sp"        /></RelativeLayout>

一定要引入 xmlns:custom=”http://schemas.android.com/apk/res/com.example.myapplication”我们的命名空间，后面的包路径指的是项目的包名。
效果如下：

本文是学习鸿洋_Hongyang大神的自定义View所写的小笔记，感谢大神，鸿洋_博客：http://blog.csdn.net/lmj623565791/article/details/24252901