android只绘制一部分图片的解决方法

两种方法:

1. canvas.drawBitmap(mBitmap, mSrcRect, mDestRect, mBitPaint);

2. canvas.clipRect

package com.abilix.learn.dashpinyinisland1.view;

import android.content.Context;
import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.drawable.BitmapDrawable;
import android.util.AttributeSet;
import android.view.View;

import com.abilix.learn.dashpinyinisland1.R;


/**
 * yhd
 * 17.7.14
 */

public class DrawBitmapView extends View {
    private Resources mResources;
    private Paint mBitPaint;
    private Bitmap mBitmap;
    private Rect mSrcRect, mDestRect;

    // view 的宽高
    private int mTotalWidth, mTotalHeight;
    private int mBitWidth;
    private int mBitHeight;

    public DrawBitmapView(Context context) {
        this(context, null);
    }

    public DrawBitmapView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mResources = getResources();
        initBitmap();
        initPaint();
    }

    public DrawBitmapView(Context context, AttributeSet attrs, int defStyleAttr) {
        this(context, attrs);
    }

    private void initPaint() {
        mBitPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        mBitPaint.setFilterBitmap(true);
        mBitPaint.setDither(true);
    }

    private void initBitmap() {
        mBitmap = ((BitmapDrawable) mResources.getDrawable(R.mipmap.sv_background_bright)).getBitmap();
        mBitWidth = mBitmap.getWidth();
        mBitHeight = mBitmap.getHeight();

        //方法一:选择绘画区域为下半图  选择绘画内容为下半图
        mSrcRect = new Rect(0, mBitHeight / 2, mBitWidth, mBitHeight);
        mDestRect = new Rect(0, mBitHeight / 2, mBitWidth, mBitHeight);


    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        //方法一:绘制
//        canvas.drawBitmap(mBitmap, mSrcRect, mDestRect, mBitPaint);

        //方法二:裁剪
        canvas.clipRect(0, mBitHeight/2, mBitWidth, mBitHeight);
        canvas.drawBitmap(mBitmap, 0, 0, mBitPaint);

    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);
        mTotalWidth = w;
        mTotalHeight = h;
    }
}