我是android的新手。今天我尝试了以下示例，但我无法继续进行。因为我在使用 nexus 5 时遇到以下错误。
错误 ：
06-12 14:52:01.348 20269-20269/com.example.imageuploader.app E/BitmapFactory﹕ Unable to decode stream: java.lang.NullPointerException
我在这个程序中遇到的任何问题。请建议
示例程序
package com.example.imageuploader.app;
import android.app.Activity;
import android.app.ProgressDialog;
import android.content.Intent;
import android.database.Cursor;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
public class MainActivity extends Activity implements OnClickListener{
private TextView messageText;
private Button uploadButton, btnselectpic;
private ImageView imageview;
private int serverResponseCode = 0;
private ProgressDialog dialog = null;
private String upLoadServerUri = null;
private String imagepath=null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
uploadButton = (Button)findViewById(R.id.uploadButton);
messageText = (TextView)findViewById(R.id.messageText);
btnselectpic = (Button)findViewById(R.id.button_selectpic);
imageview = (ImageView)findViewById(R.id.imageView_pic);
btnselectpic.setOnClickListener(this);
uploadButton.setOnClickListener(this);
upLoadServerUri = "http://192.168.0.15/UploadToServer.php";
}
@Override
public void onClick(View arg0) {
if(arg0==btnselectpic)
{
Intent intent = new Intent();
intent.setType("image/*");
intent.setAction(Intent.ACTION_GET_CONTENT);
startActivityForResult(Intent.createChooser(intent, "Complete action using"), 1);
}
else if (arg0==uploadButton) {
dialog = ProgressDialog.show(MainActivity.this, "", "Uploading file...", true);
messageText.setText("uploading started.....");
new Thread(new Runnable() {
public void run() {
uploadFile(imagepath);
}
}).start();
}
}
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
if (requestCode == 1 && resultCode == RESULT_OK) {
//Bitmap photo = (Bitmap) data.getData().getPath();
Uri selectedImageUri = data.getData();
imagepath = getPath(selectedImageUri);
Bitmap bitmap=BitmapFactory.decodeFile(imagepath);
imageview.setImageBitmap(bitmap);
messageText.setText("Uploading file path:" +imagepath);
}
}
public String getPath(Uri uri) {
String[] projection = { MediaStore.Images.Media.DATA };
Cursor cursor = getContentResolver().query(uri, new String[] { android.provider.MediaStore.Images.ImageColumns.DATA }, null, null, null);
cursor.moveToFirst();
return cursor.getString(0);
}
public int uploadFile(String sourceFileUri) {
String fileName = sourceFileUri;
HttpURLConnection conn = null;
DataOutputStream dos = null;
String lineEnd = "\r\n";
String twoHyphens = "--";
String boundary = "*****";
int bytesRead, bytesAvailable, bufferSize;
byte[] buffer;
int maxBufferSize = 1 * 1024 * 1024;
File sourceFile = new File(sourceFileUri);
if (!sourceFile.isFile()) {
dialog.dismiss();
Log.e("uploadFile", "Source File not exist :"+imagepath);
runOnUiThread(new Runnable() {
public void run() {
messageText.setText("Source File not exist :"+ imagepath);
}
});
return 0;
}
else
{
try {
// open a URL connection to the Servlet
FileInputStream fileInputStream = new FileInputStream(sourceFile);
URL url = new URL(upLoadServerUri);
// Open a HTTP connection to the URL
conn = (HttpURLConnection) url.openConnection();
conn.setDoInput(true); // Allow Inputs
conn.setDoOutput(true); // Allow Outputs
conn.setUseCaches(false); // Don't use a Cached Copy
conn.setRequestMethod("POST");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setRequestProperty("ENCTYPE", "multipart/form-data");
conn.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
conn.setRequestProperty("uploaded_file", fileName);
dos = new DataOutputStream(conn.getOutputStream());
dos.writeBytes(twoHyphens + boundary + lineEnd);
dos.writeBytes("Content-Disposition: form-data; name=\"uploaded_file\";filename=\""
+ fileName + "\"" + lineEnd);
dos.writeBytes(lineEnd);
// create a buffer of maximum size
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
buffer = new byte[bufferSize];
// read file and write it into form...
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
while (bytesRead > 0) {
dos.write(buffer, 0, bufferSize);
bytesAvailable = fileInputStream.available();
bufferSize = Math.min(bytesAvailable, maxBufferSize);
bytesRead = fileInputStream.read(buffer, 0, bufferSize);
}
// send multipart form data necesssary after file data...
dos.writeBytes(lineEnd);
dos.writeBytes(twoHyphens + boundary + twoHyphens + lineEnd);
// Responses from the server (code and message)
serverResponseCode = conn.getResponseCode();
String serverResponseMessage = conn.getResponseMessage();
Log.i("uploadFile", "HTTP Response is : "
+ serverResponseMessage + ": " + serverResponseCode);
if(serverResponseCode == 200){
runOnUiThread(new Runnable() {
public void run() {
String msg = "File Upload Completed.\n\n See uploaded file here : \n\n"
+" F:/wamp/wamp/www/uploads";
messageText.setText(msg);
Toast.makeText(MainActivity.this, "File Upload Complete.", Toast.LENGTH_SHORT).show();
}
});
}
//close the streams //
fileInputStream.close();
dos.flush();
dos.close();
} catch (MalformedURLException ex) {
dialog.dismiss();
ex.printStackTrace();
runOnUiThread(new Runnable() {
public void run() {
messageText.setText("MalformedURLException Exception : check script url.");
Toast.makeText(MainActivity.this, "MalformedURLException", Toast.LENGTH_SHORT).show();
}
});
Log.e("Upload file to server", "error: " + ex.getMessage(), ex);
} catch (Exception e) {
dialog.dismiss();
e.printStackTrace();
runOnUiThread(new Runnable() {
public void run() {
messageText.setText("Got Exception : see logcat ");
Toast.makeText(MainActivity.this, "Got Exception : see logcat ", Toast.LENGTH_SHORT).show();
}
});
Log.e("Upload file to server Exception", "Exception : " + e.getMessage(), e);
}
dialog.dismiss();
return serverResponseCode;
} // End else block
}
}
日志错误：
06-12 15:20:53.138 25602-25602/com.example.imageuploader.app D/AndroidRuntime﹕ Shutting down VM
06-12 15:20:53.138 25602-25602/com.example.imageuploader.app W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41596ba8)
06-12 15:20:53.148 25602-25602/com.example.imageuploader.app E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.imageuploader.app, PID: 25602
java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { dat=content://com.google.android.apps.docs.storage/document/acc=1;doc=677 flg=0x1 }} to activity {com.example.imageuploader.app/com.example.imageuploader.app.MainActivity}: java.lang.IllegalArgumentException: Unknown column requested: _data
at android.app.ActivityThread.deliverResults(ActivityThread.java:3351)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:3394)
at android.app.ActivityThread.access$1300(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.IllegalArgumentException: Unknown column requested: _data
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:167)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:137)
at android.content.ContentProviderProxy.query(ContentProviderNative.java:413)
at android.content.ContentResolver.query(ContentResolver.java:461)
at android.content.ContentResolver.query(ContentResolver.java:404)
at com.example.imageuploader.app.MainActivity.getPath(MainActivity.java:93)
at com.example.imageuploader.app.MainActivity.onActivityResult(MainActivity.java:84)
at android.app.Activity.dispatchActivityResult(Activity.java:5423)
at android.app.ActivityThread.deliverResults(ActivityThread.java:3347)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:3394)
at android.app.ActivityThread.access$1300(ActivityThread.java:135)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)