android获取网络图片的用法 BitmapFactory.decodeByteArray

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关于android获取网络图片主要是把网络图片的数据流读入到内存中然后用
1.Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length);
方法来将图片流传化为bitmap类型这样才能用到
1.imageView.setImageBitmap(bitMap);
来进行转化
在获取bitmap时候出现null
错误代码：
byte[] data = GetImageForNet.getImage(path);
int length = data.length;
Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length);
imageView.setImageBitmap(bitMap);
下面是 GetImageForNet.getImage()方法的代码清单
public static byte[] getImage(String path) throws Exception {
URL url = new URL(path);
HttpURLConnection httpURLconnection = (HttpURLConnection)url.openConnection();
httpURLconnection.setRequestMethod("GET");
httpURLconnection.setReadTimeout(6*1000);
InputStream in = null;
byte[] b = new byte[1024];
int len = -1;
if (httpURLconnection.getResponseCode() == 200) {
in = httpURLconnection.getInputStream();
in.read(b);
in.close();
return b;
}
return null;
}
看起来没有问题获取网络图片输入流，填充二进制数组，返回二进制数组，然后使用 Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length); data就是返回的二进制数组
获取bitMap 看起来没有问题，可是bitMap就是为null！
BitmapFactory.decodeByteArray方法中所需要的data不一定是传统意义上的字节数组，查看android api，最后发现BitmapFactory.decodeByteArray所需要的data字节数组并不是想象中的数组！而是把输入流传化为字节内存输出流的字节数组格式
正确代码：
try {
byte[] data = GetImageForNet.getImage(path);
String d = new String(data);
// File file = new File("1.jpg");
//OutputStream out = new FileOutputStream(file);
//out.write(data);
//out.close();
int length = data.length;
Bitmap bitMap = BitmapFactory.decodeByteArray(data, 0, length);
imageView.setImageBitmap(bitMap);
//imageView.seti
} catch (Exception e) {
Log.i(TAG, e.toString());
Toast.makeText(DataActivity.this, "获取图片失败", 1).show();
}
下面是改进后的 GetImageForNet.getImage()方法的代码清单
public static byte[] getImage(String path) throws Exception {
URL url = new URL(path);
HttpURLConnection httpURLconnection = (HttpURLConnection)url.openConnection();
httpURLconnection.setRequestMethod("GET");
httpURLconnection.setReadTimeout(6*1000);
InputStream in = null;
byte[] b = new byte[1024];
int len = -1;
if (httpURLconnection.getResponseCode() == 200) {
in = httpURLconnection.getInputStream();
byte[] result = readStream(in);
in.close();
return result;

}
return null;
}

public static byte[] readStream(InputStream in) throws Exception{
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len = -1;
while((len = in.read(buffer)) != -1) {
outputStream.write(buffer, 0, len);
}
outputStream.close();
in.close();
return outputStream.toByteArray();
}

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android写入数据库、读取sqlite中的图片

import java.io.ByteArrayOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import android.app.Activity;
import android.content.Context;
import android.content.res.AssetManager;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteOpenHelper;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.drawable.BitmapDrawable;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;

public class AndroidTestActivity extends Activity {
/** Called when the activity is first created. */

private Button btn;

private SQLiteDatabase db = null;

private ImageView imageView;

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

/**
* getWritableDatabase()和getReadableDatabase()方法都可以获取一个用于操作数据库的SQLiteDatabase实例。
* 但getWritableDatabase() 方法以读写方式打开数据库，一旦数据库的磁盘空间满了，数据库就只能读而不能写，
* 倘若使用getWritableDatabase()打开数据库就会出错。getReadableDatabase()方法先以读写方式打开数据库，
* 如果数据库的磁盘空间满了，就会打开失败，当打开失败后会继续尝试以只读方式打开数据库。
*/
DBHelper helper = new DBHelper(AndroidTestActivity.this, "mysql1.txt");
db = helper.getWritableDatabase();

imageView=(ImageView)findViewById(R.id.imgView);
btn=(Button)findViewById(R.id.button1);
btn.setOnClickListener(

new Button.OnClickListener()
{
public void onClick(View v)
{
String fileName="mysql.db";
AssetManager assets = getAssets();
try {
InputStream is=assets.open(fileName);

Log.v("is.length", is.available()+"");

FileOutputStream fos=new FileOutputStream(Environment.getDataDirectory()+ "/data/com.xujie.test/databases/" + "mysql1.txt");

byte[]bytes=getInput(is);

// int b=0;

// while((b=is.read())!=-1)
// {
// fos.write(b);
// }
fos.write(bytes);

/**
* 将数据流关闭
*/

fos.flush();
fos.close();
is.close();

} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

Cursor cursor= get_equipment_by_id("3");

while(cursor.moveToNext())
{
Bitmap bitmap=getIconFromCursor(cursor, cursor.getColumnIndex("icon"));

Drawable drawable=new BitmapDrawable(bitmap);

imageView.setImageDrawable(drawable);
}
}
}
);
}

public Bitmap getIconFromCursor(Cursor c, int iconIndex) {
byte[] data = c.getBlob(iconIndex);
try {

Log.v("BitmapFactory.decodeByteArray.length000:", "BitmapFactory.decodeByteArray.length");
Log.v("BitmapFactory.decodeByteArray.length:", BitmapFactory.decodeByteArray(data, 0, data.length).getWidth()+"");
Log.v("BitmapFactory.decodeByteArray.length111:", "BitmapFactory.decodeByteArray.length");

return BitmapFactory.decodeByteArray(data, 0, data.length);
} catch (Exception e) {
return null;
}
}

public byte[] getInput(InputStream is) throws IOException
{
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] b = new byte[1024];
int len = 0;

while ((len = is.read(b, 0, 1024)) != -1)
{
baos.write(b, 0, len);
baos.flush();
}
return baos.toByteArray();
}

/**
* @name get_equipment_by_id
* @desc 设备列表
* @author liwang
* @date 2011-12-28
* @paramString type 设备类型
* @return Cursor
*/
public Cursor get_equipment_by_id(String id)
{
return db.query("equipments", null, "id=?", new String[]{id} ,null, null, null);
}
class DBHelper extends SQLiteOpenHelper
{

public DBHelper(Context context, String name, CursorFactory factory, int version)
{
super(context, name, factory, version);
// TODO Auto-generated constructor stub
}
public DBHelper(Context context, String name)
{
super(context, name, null, 1);
}
@Override
public void onCreate(SQLiteDatabase db)
{
// TODO Auto-generated method stub
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion)
{
// TODO Auto-generated method stub
}
}
}

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