我尝试在字符串中加载文本文件。所以我在google搜索了一个示例代码：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;
public class AndroidInternetTxt extends Activity {
TextView textMsg, textPrompt;
final String textSource = "http://sites.google.com/site/androidersite/text.txt";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textPrompt = (TextView)findViewById(R.id.textprompt);
textMsg = (TextView)findViewById(R.id.textmsg);
textPrompt.setText("Wait...");
URL textUrl;
try {
textUrl = new URL(textSource);
BufferedReader bufferReader = new BufferedReader(new InputStreamReader(textUrl.openStream()));
String StringBuffer;
String stringText = "";
while ((StringBuffer = bufferReader.readLine()) != null) {
stringText += StringBuffer;
}
bufferReader.close();
textMsg.setText(stringText);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
textMsg.setText(e.toString());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
textMsg.setText(e.toString());
}
textPrompt.setText("Finished!");
}
}
我把它放在我的项目中现在它看起来如此：
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.entity.BufferedHttpEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import net.sourceforge.zbar.Config;
import net.sourceforge.zbar.Image;
import net.sourceforge.zbar.ImageScanner;
import net.sourceforge.zbar.Symbol;
import net.sourceforge.zbar.SymbolSet;
import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.app.Activity;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.FrameLayout;
import android.widget.Button;
import android.hardware.Camera;
import android.hardware.Camera.PreviewCallback;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.Parameters;
import android.hardware.Camera.Size;
import android.widget.TextView;
import android.graphics.ImageFormat;
public class ScannerFragment extends Fragment{
//public MainActivity(){}
private Camera mCamera;
private CameraPreview mPreview;
private Handler autoFocusHandler;
private static final String TAG_PID = "pid";
TextView scanText;
ImageScanner scanner;
private boolean barcodeScanned = false;
private boolean previewing = true;
FrameLayout preview;
final String textSource = "http://www.example.com/mytxt.txt";
static {
System.loadLibrary("iconv");
}
public void onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View android = inflater.inflate(R.layout.fragment_scanner, container, false);
autoFocusHandler = new Handler();
mCamera = getCameraInstance();
mPreview = new CameraPreview(this.getActivity(), mCamera, previewCb, autoFocusCB);
preview = (FrameLayout) android.findViewById(R.id.cameraPreview);
preview.addView(mPreview);
scanner = new ImageScanner();
scanText = (TextView) android.findViewById(R.id.scanText);
SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
String key2 = sharedPref.getString("key_data", "");
scanText.setText("barcode result old "+ key2);
return android;
}
public void onPause() {
super.onPause();
releaseCamera();
}
/** A safe way to get an instance of the Camera object. */
public static Camera getCameraInstance(){
Camera c = null;
try {
c = Camera.open();
} catch (Exception e){
}
return c;
}
private void releaseCamera() {
if (mCamera != null) {
previewing = false;
mCamera.setPreviewCallback(null);
mCamera.release();
mCamera = null;
}
}
private Runnable doAutoFocus = new Runnable() {
public void run() {
if (previewing)
mCamera.autoFocus(autoFocusCB);
}
};
PreviewCallback previewCb = new PreviewCallback() {
public void onPreviewFrame(byte[] data, Camera camera) {
Camera.Parameters parameters = camera.getParameters();
Size size = parameters.getPreviewSize();
Image barcode = new Image(size.width, size.height, "Y800");
barcode.setData(data);
int result = scanner.scanImage(barcode);
if (result != 0) {
previewing = false;
mCamera.setPreviewCallback(null);
mCamera.stopPreview();
SymbolSet syms = scanner.getResults();
for (Symbol sym : syms) {
URL textUrl;
try {
textUrl = new URL(textSource);
BufferedReader bufferReader = new BufferedReader(new InputStreamReader(textUrl.openStream()));
String StringBuffer;
String stringText = "";
while ((StringBuffer = bufferReader.readLine()) != null) {
stringText += StringBuffer;
}
bufferReader.close();
scanText.setText(stringText);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
scanText.setText(e.toString());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
scanText.setText(e.toString());
}
//StringBuilder tv = new StringBuilder();
Log.d("test", "voher");
Log.d("test", "nachher");
//scanText.setText("barcode result " + sym.getData());
String key = sym.getData();
SharedPreferences sharedPref = getActivity().getPreferences(Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPref.edit();
editor.putString("key_data", sym.getData());
editor.commit();
String str = sharedPref.getString("key_server", "");
Log.d("test", "voher");
//if (key.equals(str)){
//scanText.setText("ist richtig");
// }else{
// scanText.setText("ist falsch");
//
// }
barcodeScanned = true;
}
}
}
};
// Mimic continuous auto-focusing
AutoFocusCallback autoFocusCB = new AutoFocusCallback() {
public void onAutoFocus(boolean success, Camera camera) {
autoFocusHandler.postDelayed(doAutoFocus, 1000);
}
};
}
现在我在日志中收到一个错误：
08-24 11:31:19.096: E/AndroidRuntime(6845): FATAL EXCEPTION: main
08-24 11:31:19.096: E/AndroidRuntime(6845): Process: de.webdesign_schoenefeld.europaschule, PID: 6845
08-24 11:31:19.096: E/AndroidRuntime(6845): android.os.NetworkOnMainThreadException
08-24 11:31:19.096: E/AndroidRuntime(6845): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1156)
08-24 11:31:19.096: E/AndroidRuntime(6845): at java.net.InetAddress.lookupHostByName(InetAddress.java:385)
08-24 11:31:19.096: E/AndroidRuntime(6845): at java.net.InetAddress.getAllByNameImpl(InetAddress.java:236)
08-24 11:31:19.096: E/AndroidRuntime(6845): at java.net.InetAddress.getAllByName(InetAddress.java:214)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.Dns$1.getAllByName(Dns.java:28)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.RouteSelector.resetNextInetSocketAddress(RouteSelector.java:216)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.RouteSelector.next(RouteSelector.java:122)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:390)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.HttpEngine.sendSocketRequest(HttpEngine.java:343)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:289)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:345)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.HttpURLConnectionImpl.getResponse(HttpURLConnectionImpl.java:296)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.okhttp.internal.http.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:179)
08-24 11:31:19.096: E/AndroidRuntime(6845): at java.net.URL.openStream(URL.java:470)
08-24 11:31:19.096: E/AndroidRuntime(6845): at de.webdesign_schoenefeld.europaschule.ScannerFragment$2.onPreviewFrame(ScannerFragment.java:144)
08-24 11:31:19.096: E/AndroidRuntime(6845): at android.hardware.Camera$EventHandler.handleMessage(Camera.java:1013)
08-24 11:31:19.096: E/AndroidRuntime(6845): at android.os.Handler.dispatchMessage(Handler.java:102)
08-24 11:31:19.096: E/AndroidRuntime(6845): at android.os.Looper.loop(Looper.java:157)
08-24 11:31:19.096: E/AndroidRuntime(6845): at android.app.ActivityThread.main(ActivityThread.java:5335)
08-24 11:31:19.096: E/AndroidRuntime(6845): at java.lang.reflect.Method.invokeNative(Native Method)
08-24 11:31:19.096: E/AndroidRuntime(6845): at java.lang.reflect.Method.invoke(Method.java:515)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
08-24 11:31:19.096: E/AndroidRuntime(6845): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
08-24 11:31:19.096: E/AndroidRuntime(6845): at dalvik.system.NativeStart.main(Native Method)
当我在URL之前删除http://我得到文本“java error not find protocol”
编辑1：
第70行
scanText = (TextView)getView().findViewById(R.id.scanText);
Stacktrace：
08-24 12:30:33.846: E/MoreInfoHPW_ViewGroup(15791): Parent view is not a TextView
08-24 12:30:36.716: E/AndroidRuntime(15791): FATAL EXCEPTION: main
08-24 12:30:36.716: E/AndroidRuntime(15791): Process: de.webdesign_schoenefeld.europaschule, PID: 15791
08-24 12:30:36.716: E/AndroidRuntime(15791): java.lang.NullPointerException
08-24 12:30:36.716: E/AndroidRuntime(15791): at de.webdesign_schoenefeld.europaschule.ScannerFragment.onCreate(ScannerFragment.java:70)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.Fragment.performCreate(Fragment.java:1678)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:859)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.BackStackRecord.run(BackStackRecord.java:684)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.FragmentManagerImpl$1.run(FragmentManager.java:443)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.os.Handler.handleCallback(Handler.java:733)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.os.Handler.dispatchMessage(Handler.java:95)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.os.Looper.loop(Looper.java:157)
08-24 12:30:36.716: E/AndroidRuntime(15791): at android.app.ActivityThread.main(ActivityThread.java:5335)
08-24 12:30:36.716: E/AndroidRuntime(15791): at java.lang.reflect.Method.invokeNative(Native Method)
08-24 12:30:36.716: E/AndroidRuntime(15791): at java.lang.reflect.Method.invoke(Method.java:515)
08-24 12:30:36.716: E/AndroidRuntime(15791): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
08-24 12:30:36.716: E/AndroidRuntime(15791): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
08-24 12:30:36.716: E/AndroidRuntime(15791): at dalvik.system.NativeStart.main(Native Method)
答案 0 :(得分：1)
如果您正在主线程（即ui线程）上进行网络操作，则在聊天http://chat.stackoverflow.com/rooms/59874/discussion-between-marius-schonefeld-and-raghunandan中发生NetWorkOnMainThreadException的讨论。
你要求的3个参数
- Params，执行时发送给任务的参数类型。
- 进度，后台计算期间发布的进度单位的类型。
- 结果，背景计算结果的类型。
示例：
public class AndroidInternetTxt extends Activity {
TextView textMsg, textPrompt;
final String textSource = "http://sites.google.com/site/androidersite/text.txt";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
textPrompt = (TextView)findViewById(R.id.textprompt);
textMsg = (TextView)findViewById(R.id.textmsg);
textPrompt.setText("Wait...");
new TheTask().execute("http://sites.google.com/site/androidersite/text.txt");
}
private class TheTask extends AsyncTask<String,Void,String>
{
protected String doInBackground(String... args)
{
URL textUrl;
String stringText = "";
try {
textUrl = new URL(args[0]);
BufferedReader bufferReader = new BufferedReader(new InputStreamReader(textUrl.openStream()));
String StringBuffer;
while ((StringBuffer = bufferReader.readLine()) != null) {
stringText += StringBuffer;
}
bufferReader.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return stringText;
}
protected void onPostExecute(String result)
{
super.onPostExecute(result);
textPrompt.setText(result);
}
}
}
编辑1：
更改此
scanText = (TextView)getView().findViewById(R.id.scanText);
到
scanText = (TextView)getActivity().findViewById(R.id.scanText);