在我的 Android 应用程序中，我正在调用一个 Java Web 服务，它返回一个 Image Blob。我想在 ImageView 中将其显示为位图。此图像 blob 是 HTML5 Canvas 元素的已保存 toDataUrl() 表示。主线程将 AsyncTask 内部类作为带有执行命令的 onclick 启动。这是主线程：
public class MainActivity extends Activity
{
private ImageView outputIv;
public View vue;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setOutputIv((ImageView)findViewById(R.id.imageView1));
}
public void onClickBtn(View v){
vue = v;
new RequestTask(v).execute("http://10.0.2.2:8080/CasosDeUso5/webresources/casosdeusowsport/getimagenes?usuarioId=1");
}
/**
* @return the outputIv
*/
public ImageView getOutputIv() {
return outputIv;
}
/**
* @param outputIv the outputIv to set
*/
public void setOutputIv(ImageView outputIv) {
this.outputIv = outputIv;
}
class RequestTask extends AsyncTask<String, String, String>{
private View rootView;
public RequestTask(View rootView){
this.rootView=rootView;
}
@Override
protected String doInBackground(String... uri) {
HttpClient httpclient = new DefaultHttpClient();
HttpResponse response;
String responseString = "STRAWBERRIES";
try {
response = httpclient.execute(new HttpGet(uri[0]));
StatusLine statusLine = response.getStatusLine();
Log.d("info", statusLine.toString());
if(statusLine.getStatusCode() == HttpStatus.SC_OK){
ByteArrayOutputStream out = new ByteArrayOutputStream();
response.getEntity().writeTo(out);
out.close();
responseString = out.toString();
} else{
//Closes the connection.
response.getEntity().getContent().close();
throw new IOException(statusLine.getReasonPhrase());
}
} catch (ClientProtocolException e) {
Log.d("OH CRIKEY", e.toString());
} catch (IOException e) {
Log.d("OH CRIKEY", e.toString());
}
Log.d("info", responseString);
return responseString;
}
@Override
protected void onPostExecute(String result) {
//super.onPostExecute(result);
try{
List<Imagen> imgs = Parser.parseByDOM(result);
//Below prints 3280
Log.d("UUYU", String.valueOf(imgs.get(0).getImagen().getRowBytes()));
//Below prints 550
Log.d("UUYU2", String.valueOf(imgs.get(0).getImagen().getHeight()));
//Below prints 820
Log.d("UUYU3", String.valueOf(imgs.get(0).getImagen().getWidth()));
outputIv.setImageBitmap(imgs.get(0).getImagen());
//vue.invalidate();
}catch(Exception e){ e.printStackTrace();
Log.d("ERROR!!", ""+e.getMessage());}
//outputTv.setText(result);
}
/**
* @return the rootView
*/
public View getRootView() {
return rootView;
}
/**
* @param rootView the rootView to set
*/
public void setRootView(View rootView) {
this.rootView = rootView;
}
}
位图具有正确的宽度和高度，并且似乎有数据。这是我解析 Web 服务响应字符串并设置位图的地方，只是为了完整性。所有的调试看起来都很好。
public static List<Imagen> parseByDOM(String response) throws ParserConfigurationException, SAXException, IOException{
DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
DocumentBuilder db = dbf.newDocumentBuilder();
Document doc = db.parse(new InputSource(new StringReader(response)));
// normalize the document
doc.getDocumentElement().normalize();
// get the root node
NodeList nodeList = doc.getElementsByTagName("return");
Log.d("miaouw", nodeList.toString());
List<Imagen> imgData = new ArrayList<Imagen>();
for(int k = 0; k < nodeList.getLength(); k++){
Node node=nodeList.item(0);
Log.d("miaouw", node.getNodeName());
Imagen img = new Imagen();
try{
for(int i = 0; i < node.getChildNodes().getLength(); i++){
Node temp = node.getChildNodes().item(i);
Log.d("miaouw", temp.getNodeName());
if(temp.getNodeName().equalsIgnoreCase("fechaCreada")){
img.setFechaCreada(new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss", Locale.ENGLISH).parse(temp.getTextContent()));
}
else if(temp.getNodeName().equalsIgnoreCase("imagen")){
String encodedImg = temp.getTextContent();
Log.d("vroom", encodedImg); //prints long, correct base64 binary String. If I try to convert it to an image in http://www.freeformatter.com/base64-encoder.html, I get the correct image.
Log.d("toom ", String.valueOf(encodedImg.length())); //prints 19383
byte[] decodedString = Base64.decode(encodedImg, Base64.DEFAULT);
Log.d("woom", decodedString.toString()); //prints B@417b72f0
Bitmap decodedByte = BitmapFactory.decodeByteArray(decodedString, 0, decodedString.length);
img.setImagen(decodedByte);
}
else if(temp.getNodeName().equalsIgnoreCase("titulo")){
img.setTitulo(temp.getTextContent());
}
}
imgData.add(img);
Log.d("MIAUOW", img.toString()); //prints com.example.android.Imagen@4175ec58
Log.d("noddy", node.toString());
return imgData;
}catch(ParseException e){
Log.d("MEWL", e.getMessage());
}
}
return null;
}
最后，这是我的布局。我将 ImageView 设置为默认的 Android drawable 只是为了确保视图正在更新（因为它是异步的）。当我单击测试时，src 图像消失了，但它没有被我的位图替换。
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<Button
android:id="@+id/button1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="Test"
android:onClick="onClickBtn" />
<ImageView
android:id="@+id/imageView1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:contentDescription="yep"
android:src="@drawable/ic_launcher"/>
</LinearLayout>
这意味着作为一个简单的概念证明，但它不起作用。我不明白位图是如何存在的，并且视图会更新，但位图是不可见的。