Api Demo - .graphics(10)

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.graphics;

//Need the following import to get access to the app resources, since this
//class is in a sub-package.
import com.example.android.apis.R;

import android.app.Activity;
import android.os.Bundle;
import android.graphics.BitmapFactory;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.widget.LinearLayout;
import android.widget.TextView;
import android.widget.ScrollView;
import android.view.LayoutInflater;
import android.view.View;
import android.content.Context;
import android.util.DisplayMetrics;
import android.util.Log;

/**
 * This activity demonstrates various ways density can cause the scaling of
 * bitmaps and drawables.
 */
public class DensityActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        final LayoutInflater li = (LayoutInflater)getSystemService(
                LAYOUT_INFLATER_SERVICE);//获取布局泵
        
        this.setTitle(R.string.density_title);
        LinearLayout root = new LinearLayout(this);
        root.setOrientation(LinearLayout.VERTICAL);

        LinearLayout layout = new LinearLayout(this);
        addBitmapDrawable(layout, R.drawable.logo120dpi, true);
        addBitmapDrawable(layout, R.drawable.logo160dpi, true);
        addBitmapDrawable(layout, R.drawable.logo240dpi, true);
        addLabelToRoot(root, "Prescaled bitmap in drawable");
        addChildToRoot(root, layout);

        layout = new LinearLayout(this);
        addBitmapDrawable(layout, R.drawable.logo120dpi, false);
        addBitmapDrawable(layout, R.drawable.logo160dpi, false);
        addBitmapDrawable(layout, R.drawable.logo240dpi, false);
        addLabelToRoot(root, "Autoscaled bitmap in drawable");
        addChildToRoot(root, layout);

        layout = new LinearLayout(this);
        addResourceDrawable(layout, R.drawable.logo120dpi);
        addResourceDrawable(layout, R.drawable.logo160dpi);
        addResourceDrawable(layout, R.drawable.logo240dpi);
        addLabelToRoot(root, "Prescaled resource drawable");
        addChildToRoot(root, layout);

        layout = (LinearLayout)li.inflate(R.layout.density_image_views, null);//从XML文件读取布局
        addLabelToRoot(root, "Inflated layout");
        addChildToRoot(root, layout);
        
        layout = (LinearLayout)li.inflate(R.layout.density_styled_image_views, null);//从XML文件读取布局，属性通过style同意设置
        addLabelToRoot(root, "Inflated styled layout");
        addChildToRoot(root, layout);
        
        
        /*
         * Android系统根据当前设备屏幕配置不进行缩放选取设备配置相关的资源
         * drawable 文件夹不带任何后缀，为缺省drawable 资源， 
         * drawable-hdpi 为高密度屏幕使用的drawable资源drawable-hdpi 为低密度屏幕使用的drawable-ldpi 资源等。
         * 同样values 定义了多种不同配置下使用的资源。
         * 对应不同屏幕密度下的Bitmap资源定义(.png. .jpg, .gif ,.9.png)
         * 一个原则上使用 3:4:6:8的比例来为四种不同屏幕密度提供图像资源，
         * 比如对于一个“中等密度”下像素大小为48X48的资源，
         * Low-density:  36X36
         * Medium-density: 48X48
         * High-density: 72X72
         * Extra high-density: 96X96
         * 系统会根据当前屏幕密度从对应的文件夹里提取资源文件，当资源缺失则，会从其他文件夹读取，顺序如下
         * 优先默认文件夹drawable,没有资源则从最小密度的文件夹向上读取，读取的文件会根据文件夹对应密度自动按比值缩放。
         * 比如当前屏幕密度为160，如果资源图片放在drawable-ldpi,图片会自动放大。如果放在drawable-hdpi会自动缩小。
         * 本列有两种有两种方法禁止自动缩放：
         * 第一种是将图片放在drawable-nodpi文件目录，
         * 第二种是将opts.inScaled = false。
         */
        
        layout = new LinearLayout(this);
        addCanvasBitmap(layout, R.drawable.logo120dpi, true);
        addCanvasBitmap(layout, R.drawable.logo160dpi, true);
        addCanvasBitmap(layout, R.drawable.logo240dpi, true);
        addLabelToRoot(root, "Prescaled bitmap");
        addChildToRoot(root, layout);

        layout = new LinearLayout(this);
        addCanvasBitmap(layout, R.drawable.logo120dpi, true);
        addCanvasBitmap(layout, R.drawable.logo160dpi, true);
        addCanvasBitmap(layout, R.drawable.logo240dpi, true);
        addLabelToRoot(root, "Autoscaled bitmap");
        addChildToRoot(root, layout);

        layout = new LinearLayout(this);
        addResourceDrawable(layout, R.drawable.logonodpi120);
        addResourceDrawable(layout, R.drawable.logonodpi160);
        addResourceDrawable(layout, R.drawable.logonodpi240);
        addLabelToRoot(root, "No-dpi resource drawable");
        addChildToRoot(root, layout);

        layout = new LinearLayout(this);
        addNinePatchResourceDrawable(layout, R.drawable.smlnpatch120dpi);
        addNinePatchResourceDrawable(layout, R.drawable.smlnpatch160dpi);
        addNinePatchResourceDrawable(layout, R.drawable.smlnpatch240dpi);
        addLabelToRoot(root, "Prescaled 9-patch resource drawable");
        addChildToRoot(root, layout);

        setContentView(scrollWrap(root));
    }

    private View scrollWrap(View view) {
        ScrollView scroller = new ScrollView(this);
        scroller.addView(view, new ScrollView.LayoutParams(ScrollView.LayoutParams.MATCH_PARENT,
                ScrollView.LayoutParams.MATCH_PARENT));
        return scroller;
    }

    private void addLabelToRoot(LinearLayout root, String text) {//往Layout动态添加View
        TextView label = new TextView(this);
        label.setText(text);
        root.addView(label, new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.WRAP_CONTENT));
    }

    private void addChildToRoot(LinearLayout root, LinearLayout layout) {//往Layout动态添加Layout,
        root.addView(layout, new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT,
                LinearLayout.LayoutParams.WRAP_CONTENT));
    }

    private void addBitmapDrawable(LinearLayout layout, int resource, boolean scale) {//以BitmapDrawable将图片设成背景
        Bitmap bitmap;
        bitmap = loadAndPrintDpi(resource, scale);

        View view = new View(this);

        final BitmapDrawable d = new BitmapDrawable(getResources(), bitmap);
        if (!scale) d.setTargetDensity(getResources().getDisplayMetrics());
        view.setBackgroundDrawable(d);

        view.setLayoutParams(new LinearLayout.LayoutParams(d.getIntrinsicWidth(),
                d.getIntrinsicHeight()));
        layout.addView(view);
    }

    private void addResourceDrawable(LinearLayout layout, int resource) {//以Drawable将图片设成背景
        View view = new View(this);

        final Drawable d = getResources().getDrawable(resource);
        view.setBackgroundDrawable(d);

        view.setLayoutParams(new LinearLayout.LayoutParams(d.getIntrinsicWidth(),
                d.getIntrinsicHeight()));
        layout.addView(view);
    }

    private void addCanvasBitmap(LinearLayout layout, int resource, boolean scale) {//以BitmapDrawable将图片设成背景
        Bitmap bitmap;
        bitmap = loadAndPrintDpi(resource, scale);

        ScaledBitmapView view = new ScaledBitmapView(this, bitmap);

        view.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT,
                LinearLayout.LayoutParams.WRAP_CONTENT));
        layout.addView(view);
    }

    private void addNinePatchResourceDrawable(LinearLayout layout, int resource) {
        View view = new View(this);

        final Drawable d = getResources().getDrawable(resource);
        view.setBackgroundDrawable(d);

        Log.i("foo", "9-patch #" + Integer.toHexString(resource)//以16进制转换成字符。
                + " w=" + d.getIntrinsicWidth() + " h=" + d.getIntrinsicHeight());
        view.setLayoutParams(new LinearLayout.LayoutParams(
                d.getIntrinsicWidth()*2, d.getIntrinsicHeight()*2));
        layout.addView(view);
    }

    private Bitmap loadAndPrintDpi(int id, boolean scale) {
        Bitmap bitmap;
        if (scale) {
            bitmap = BitmapFactory.decodeResource(getResources(), id);
        } else {
            BitmapFactory.Options opts = new BitmapFactory.Options();
            opts.inScaled = false;//不允许缩放。
            bitmap = BitmapFactory.decodeResource(getResources(), id, opts);
        }
        return bitmap;
    }

    private class ScaledBitmapView extends View {//自定义View,重写onMeasure，使Bitmap按比例缩放
        private Bitmap mBitmap;

        public ScaledBitmapView(Context context, Bitmap bitmap) {
            super(context);
            mBitmap = bitmap;
        }

        @Override
        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            final DisplayMetrics metrics = getResources().getDisplayMetrics();
            setMeasuredDimension(//设置显示宽高
                    mBitmap.getScaledWidth(metrics),//返回DisplayMetrics整除后的位图宽度值；
                    mBitmap.getScaledHeight(metrics));
        }
       



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

            canvas.drawBitmap(mBitmap, 0.0f, 0.0f, null);
        }
    }
}