先看代码：
public class MainActivity extends AppCompatActivity {
String TAG = MainActivity.class.getCanonicalName();
private ImageView imageview;
private Button load;
String path = "http://img06.tooopen.com/images/20161120/tooopen_sl_187242346264.jpg";
private Bitmap bitmap;
private File picfile;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
imageview = (ImageView) findViewById(R.id.imageview);
load = (Button) findViewById(R.id.btn_load);
load.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
File file = createPicfile();
if (null != file){
String absolutePath = file.getAbsolutePath();
Log.e(TAG, "onClick: "+absolutePath );
String filepath = absolutePath+getFilePath(path);
Log.e(TAG, "onClick: "+filepath );
picfile = new File(filepath);
if (picfile.exists()){
Log.e(TAG, "onClick: "+"文件存在" );
bitmap = BitmapFactory.decodeFile(picfile.getAbsolutePath());
if (null != bitmap){
Message msg = Message.obtain();
msg.what =2;
handler.sendMessage(msg);
}else {
Log.e(TAG, "onClick: "+"文件下载错误" );
}
}else {
Log.e(TAG, "onClick: "+"文件不存在" );
try {
picfile.createNewFile();
new Thread(new Runnable() {
@Override
public void run() {
loadpicture(picfile,path);
}
}).start();
} catch (IOException e) {
e.printStackTrace();
}
}
}else {
Log.e(TAG, "createPicfile: "+"没有sd卡" );
}
}
});
}
private void loadpicture(File picfile, String path) {
try {
FileOutputStream fos = new FileOutputStream(picfile);
URL url = new URL(path);
HttpURLConnection httpconn = (HttpURLConnection) url.openConnection();
httpconn.setConnectTimeout(5000);
httpconn.setRequestMethod("GET");
int code = httpconn.getResponseCode();
if (HttpURLConnection.HTTP_OK == code){
Log.e(TAG, "loadpicture: "+"正在下载、、、、" );
Log.e(TAG, "loadpicture: "+"下载文件大小:"+ httpconn.getContentLength());
InputStream is = httpconn.getInputStream();
byte[] buff = new byte[512];
int len ;
while((len = (is.read(buff))) != -1){ //刚开始时把while写成if，只会运行一次
fos.write(buff,0,len);
}
is.close();
fos.flush();
fos.close();
Log.e(TAG, "loadpicture: "+"下载完成、、" );
bitmap = BitmapFactory.decodeFile(picfile.getAbsolutePath());
if (null != bitmap) {
Message msg = Message.obtain();
msg.what = 1;
handler.sendMessage(msg);
}
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
private String getFilePath(String path) {
if (null != path){
StringBuilder builder = new StringBuilder(path.trim());
int i = builder.lastIndexOf("/");
String filepath = builder.substring(i);
return filepath;
}else {
return null;
}
}
private File createPicfile() {
if (Environment.getExternalStorageState().equals(Environment.getExternalStorageState())){
String s = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Picture";
File file = new File(s);
if (!file.exists()){
file.mkdir();
}
return file;
}else {
Log.e(TAG, "createPicfile: "+"没有sd卡" );
}
return null;
}
Handler handler = new Handler(){
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (msg.what == 1){
imageview.setImageBitmap(bitmap);
Log.e(TAG, "handleMessage: "+"网络下载图片显示 ");
}
if (msg.what == 2){
imageview.setImageBitmap(bitmap);
Log.e(TAG, "handleMessage: "+"本地获取图片显示" );
}
}
};
}
记得加权限：
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<uses-permission android:name="android.permission.INTERNET"/> demo下载地址：https://github.com/renjiemei1225/LoadImageAndSave