OOM異常解決

02-03 08:56:12.411: E/AndroidRuntime(10137): FATAL EXCEPTION: main
02-03 08:56:12.411: E/AndroidRuntime(10137): java.lang.IllegalStateException: Could not execute method of the activity
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.view.View$1.onClick(View.java:3591)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.view.View.performClick(View.java:4084)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.view.View$PerformClick.run(View.java:16966)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.os.Handler.handleCallback(Handler.java:615)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.os.Handler.dispatchMessage(Handler.java:92)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.os.Looper.loop(Looper.java:137)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.app.ActivityThread.main(ActivityThread.java:4745)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at java.lang.reflect.Method.invokeNative(Native Method)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at java.lang.reflect.Method.invoke(Method.java:511)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at dalvik.system.NativeStart.main(Native Method)
02-03 08:56:12.411: E/AndroidRuntime(10137): Caused by: java.lang.reflect.InvocationTargetException
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at java.lang.reflect.Method.invokeNative(Native Method)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at java.lang.reflect.Method.invoke(Method.java:511)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.view.View$1.onClick(View.java:3586)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	... 11 more
02-03 08:56:12.411: E/AndroidRuntime(10137): Caused by: java.lang.OutOfMemoryError
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.graphics.BitmapFactory.nativeDecodeStream(Native Method)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.graphics.BitmapFactory.decodeStream(BitmapFactory.java:527)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:301)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at android.graphics.BitmapFactory.decodeFile(BitmapFactory.java:326)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	at com.ithema.bitmap.MainActivity.down(MainActivity.java:52)
02-03 08:56:12.411: E/AndroidRuntime(10137): 	... 14 more

堆內存空間主要是給類實例、數組分配空間。當圖片佔用的空間大於對內存空間時就會拋出內存溢出的異常。

本示例是在加載15M左右的圖片而引起的OOM異常，默認情況下，虛擬機只語序允許加載10M以內大小的圖片。如果超過10M，則會拋出OOM異常

問題解決思路：縮放加載圖片
1、得到設備屏幕的分辨率：
2、得到原圖的分辨率：
3、通過比較得到一個合適的比例值：
4、使用比例值縮放一張圖片，並加載到內存中：

示例代碼：

package com.ithema.bitmap;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.BitmapFactory.Options;
import android.graphics.Point;
import android.os.Bundle;
import android.os.Environment;
import android.view.Display;
import android.view.View;
import android.view.WindowManager;
import android.widget.ImageView;

public class MainActivity extends Activity {

    private ImageView iv;
	@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        iv = (ImageView) findViewById(R.id.iv);
    }
    public void down(View view) {
		//1.獲取手機屏幕分辨率的大小
    	WindowManager wm=(WindowManager) getSystemService(WINDOW_SERVICE);
    	Display display = wm.getDefaultDisplay();
    	int screenHeight = display.getHeight();
    	int screenWidth = display.getWidth();
    	//2.獲取原圖分辨率的大小
    	Options opts=new Options();
    	opts.inJustDecodeBounds=true;
		BitmapFactory.decodeFile(Environment.getExternalStorageDirectory()+"/1.bmp", opts);
    	int outHeight = opts.outHeight;
    	int outWidth = opts.outWidth;
    	//3.得到縮放比
    	int scale=1;
    	int scaleX=outWidth/screenWidth;
    	int scaleY=outHeight/screenHeight;
    	if(scaleX>scaleY&&scaleX>1){
    		scale=scaleX;
    	}
    	if(scaleY>scaleX&&scaleY>1){
    		scale=scaleY;
    	}
    	
    	//4.使用比例值縮放一張圖片，並加載到內存中：
    	opts.inJustDecodeBounds=false;
    	opts.inSampleSize=scale;
    	Bitmap bitmap = BitmapFactory.decodeFile(Environment.getExternalStorageDirectory()+"/1.bmp", opts);
    	
    	iv.setImageBitmap(bitmap);
	}
}

佈局文件代碼：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
     >
	<Button 
	    android:onClick="down"
	    android:text="加載大圖片"
	    android:layout_width="fill_parent"
        android:layout_height="wrap_content"
	    />
    <ImageView
        android:id="@+id/iv"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />

</LinearLayout>