1 package cn.itcast.resizeimage;
 2 
 3 import java.io.FileNotFoundException;
 4 import java.io.IOException;
 5 import java.io.InputStream;
 6 
 7 import android.app.Activity;
 8 import android.content.Intent;
 9 import android.graphics.Bitmap;
10 import android.graphics.BitmapFactory;
11 import android.graphics.BitmapFactory.Options;
12 import android.net.Uri;
13 import android.os.Bundle;
14 import android.view.Display;
15 import android.view.View;
16 import android.view.WindowManager;
17 import android.widget.ImageView;
18 
19 public class LoadImageActivity extends Activity {
20     private ImageView iv;
21     private WindowManager wm;
22     private Display  display;
23     @Override
24     public void onCreate(Bundle savedInstanceState) {
25         super.onCreate(savedInstanceState);
26         setContentView(R.layout.main);
27         iv = (ImageView) findViewById(R.id.iv);
28         wm = getWindowManager();
29         //獲取手機的屏幕寬高
30         display = wm.getDefaultDisplay();
31     }
32 
33     public void selectImage(View view) {
34         Intent intent = new Intent();
35         intent.setAction("android.intent.action.PICK");
36         intent.addCategory("android.intent.category.DEFAULT");
37         intent.setType("image/*");
38         startActivityForResult(intent, 0);
39 
40     }
41 
42     @Override
43     protected void onActivityResult(int requestCode, int resultCode, Intent data) {
44         try {
45             if (data != null) {
46                 // 得到點擊圖片的uri
47                 Uri uri = data.getData();
48                 //對 要加載的圖片進行縮放
49                 //1.得到圖片的寬度和高度.
50                 //由于我們只想得到圖片的寬度和高度,這個時候 只需要解析圖片的頭信息
51                 BitmapFactory.Options opts = new Options();
52                 opts.inJustDecodeBounds = true;//讓 bimapfactory假的解析這個位圖,只獲取位圖的邊框信息
53                 InputStream is = getContentResolver().openInputStream(uri);
54                 BitmapFactory.decodeStream(is);
55                 
56                 int bitmapHeight =     opts.outHeight;
57                 int bitmapWidth = opts.outWidth;
58                 
59                 int windowHeight = display.getHeight();
60                 int windowWidth = display.getWidth();
61                 //獲取水平和垂直方向的縮放比
62                 int scaley = bitmapHeight / windowHeight;
63                 int scalex = bitmapWidth / windowWidth;
64                 if(scalex>scaley&&scaley>1){
65                     opts.inSampleSize = scalex;
66                 }
67                 if(scaley>scalex&&scalex>1){
68                     opts.inSampleSize = scaley;
69                 }
70                 opts.inJustDecodeBounds = false;// 由于已經得到了縮放比例 ,讓位圖工廠真正的解析這個位圖
71                 // 由于前面 我們已經解析了這個輸入流, 需要重新初始化這個輸入流
72                 is = getContentResolver().openInputStream(uri);
73                 Bitmap bitmap =  BitmapFactory.decodeStream(is);
74                 
75                 
76                 
77                 iv.setImageBitmap(bitmap);
78             }
79         } catch (Exception e) {
80             e.printStackTrace();
81         }
82         super.onActivityResult(requestCode, resultCode, data);
83     }
84 }