Android学习笔记（十八）：ImageView设置网络图片

方案一：读取网络图片的inputStream，然后传给bitmap，再显示在imageView中，但是实际操作的时候，提示错误：android.os.NetworkOnMainThreadException（是因为现在网络请求不允许在主线程main中执行，要另外开辟一个子线程进行）

下面是出错的将网络图片转成bitmap的方法

//将网络图片转换成bitmap
public Bitmap getHttpBitmap(String url) {
URL httpUrl = null;
Bitmap bitmap = null;
try {
httpUrl = new URL(url);
HttpURLConnection conn = (HttpURLConnection) httpUrl.openConnection();
conn.setConnectTimeout(6000);
conn.setDoInput(true);
conn.setUseCaches(false);
InputStream in = conn.getInputStream();／／这行报错
bitmap = BitmapFactory.decodeStream(in);
in.close();
} catch (Exception e) {
e.printStackTrace();
Toast.makeText(this,"系统繁忙，请稍后再试",Toast.LENGTH_SHORT).show();
}
return bitmap;

}

下面是修改后的方法：直接开辟一个子线程，然后在里面设置网络图片，并在onCreate中调用该方法即可

public void setNetworkBitmap() {
Runnable networkImg = new Runnable() {
@Override
public void run() {
try {
URL httpUrl = new URL(getIntent().getStringExtra("QRCode"));
HttpURLConnection conn = (HttpURLConnection) httpUrl.openConnection();
conn.setConnectTimeout(6000);
conn.setDoInput(true);
conn.setUseCaches(false);
InputStream in = conn.getInputStream();
bitmap = BitmapFactory.decodeStream(in);
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
};
new Thread(networkImg).start();
while(bitmap == null)
continue;
QRImg.setImageBitmap(bitmap);
}

或者下面的代码也可以，更简洁点

public void setNetworkBitmap() {
Runnable networkImg = new Runnable() {
@Override
public void run() {
try {
URL conn = new URL(getIntent().getStringExtra("QRCode"));
InputStream in = conn.openConnection().getInputStream();
bitmap = BitmapFactory.decodeStream(in);
in.close();
} catch (Exception e) {
e.printStackTrace();
}
}
};
new Thread(networkImg).start();
while(bitmap == null)
continue;
QRImg.setImageBitmap(bitmap);
}

方案二：摘自stackoverflow

http://stackoverflow.com/questions/2471935/how-to-load-an-imageview-by-url-in-android

private class DownloadImageTask extends AsyncTask<String, Void, Bitmap> {
ImageView bmImage;

public DownloadImageTask(ImageView bmImage) {
this.bmImage = bmImage;
}

protected Bitmap doInBackground(String... urls) {
String urldisplay = urls[0];
Bitmap mIcon11 = null;
try {
InputStream in = new java.net.URL(urldisplay).openStream();
mIcon11 = BitmapFactory.decodeStream(in);
} catch (Exception e) {
Log.e("Error", e.getMessage());
e.printStackTrace();
}
return mIcon11;
}

protected void onPostExecute(Bitmap result) {
bmImage.setImageBitmap(result);
}
}

然后在oncreate中执行下面的代码

new DownloadImageTask(QRImg).execute(getIntent().getStringExtra("QRCode"));