Question

 E/AndroidRuntime(15518): FATAL EXCEPTION: main
 E/AndroidRuntime(15518): java.lang.RuntimeException: Unable to instantiate activity      ComponentInfo{com.cydeon.plasmamodz/com.cydeon.plasmamodz.Boots}:     java.lang.NullPointerException
E/AndroidRuntime(15518):    at    android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2224)
 E/AndroidRuntime(15518):   at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
 E/AndroidRuntime(15518):   at android.app.ActivityThread.access$600(ActivityThread.java:154)
 E/AndroidRuntime(15518):   at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1248)
 E/AndroidRuntime(15518):   at android.os.Handler.dispatchMessage(Handler.java:99)
 E/AndroidRuntime(15518):   at android.os.Looper.loop(Looper.java:137)
 E/AndroidRuntime(15518):   at android.app.ActivityThread.main(ActivityThread.java:5235)
 E/AndroidRuntime(15518):   at java.lang.reflect.Method.invokeNative(Native Method)
 E/AndroidRuntime(15518):   at java.lang.reflect.Method.invoke(Method.java:511)
 E/AndroidRuntime(15518):   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
 E/AndroidRuntime(15518):   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
 E/AndroidRuntime(15518):   at dalvik.system.NativeStart.main(Native Method)
 E/AndroidRuntime(15518): Caused by: java.lang.NullPointerException
 E/AndroidRuntime(15518):   at android.app.Activity.findViewById(Activity.java:1839)
 E/AndroidRuntime(15518):   at com.cydeon.plasmamodz.Boots.<init>(Boots.java:47)
 E/AndroidRuntime(15518):   at java.lang.Class.newInstanceImpl(Native Method)
 E/AndroidRuntime(15518):   at java.lang.Class.newInstance(Class.java:1319)
 E/AndroidRuntime(15518):   at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
 E/AndroidRuntime(15518):   at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
 E/AndroidRuntime(15518):   ... 11 more

这个话题令人困惑。让我解释。在我的应用程序中，我只有一个部分有70多个按钮。我有很多不同的部分。现在，每个按钮使用相同的布局，因此每个按钮启动相同的活动，这样我就不会创建70个单独的类。现在，在这个新类中，它必须显示一个图像并下载一个文件（当点击某个按钮时），该文件对应于被挑选的bugton。所以，基本上，我需要一些方法来识别其他类中的那些按钮，并说“如果按下按钮x，显示图像y，如果按下按钮y，则显示图像x。同样，如果按下按钮x，则下载文件y，如果按下按钮y，下载文件x，等等。我根本不知道如何判断上一课中按下了哪个按钮。我真的需要帮助。我已经工作了2个星期了让我停下来，我找不到答案。这不是真正的代码依赖，我将在整个应用程序中多次使用此方法，所以我不认为需要发布任何代码。再次，到重申我的问题，多个按钮开始相同的活动。在那个活动中，我需要根据上一课中按下的按钮来做东西。谢谢。:)

编辑：这是一些代码......

BootFragment.java：

package com.cydeon.plasmamodz;

 import java.io.File;
 import java.io.IOException;
 import java.util.concurrent.TimeoutException;

 import com.stericson.RootTools.RootTools;
 import com.stericson.RootTools.exceptions.RootDeniedException;
 import com.stericson.RootTools.execution.CommandCapture;

 import android.app.Fragment;
 import android.content.Intent;
 import android.os.Bundle;
 import android.os.Environment;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.ViewGroup;
 import android.widget.Button;

 public class BootFragment extends Fragment {{


    //Defining File Directory
    File directory = new File(Environment.getExternalStorageDirectory() + "/plasma/boot");
    if(directory.exists() && directory.isDirectory()){
    //Do nothing. Directory is existent 
    }else{
    //Directory does not exist. Make directory (First time app users)
    directory.mkdirs();
    }

    File bkup = new File(Environment.getExternalStorageDirectory() + "/plasma/boot/bkup");
    if(bkup.exists() && bkup.isDirectory()){
    //Do nothing. Directory is existent 
    }else{
    //Directory does not exist. Make directory (First time app users)
    bkup.mkdirs();
    }}





@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
     View view = inflater.inflate(R.layout.boot_frag,
                container, false);
     Button Ablue = (Button) view.findViewById(R.id.bABlue);
     Button AblueR = (Button) view.findViewById(R.id.bABlueR);
     Button Abokeh = (Button) view.findViewById(R.id.bAbokeh);

     Ablue.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
                    Intent b = new Intent(getActivity(), Boots.class);
                    b.putExtra("Dragon", R.id.bABlue);
                    BootFragment.this.startActivity(b);
            }
            });

     AblueR.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                        Intent c = new Intent(getActivity(), Boots.class);
                        c.putExtra("Xbox", R.id.bABlueR);
                        BootFragment.this.startActivity(c);
                }
                });

     Abokeh.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View arg0) {
                        Intent d = new Intent(getActivity(), Boots.class);
                        d.putExtra("GameB", R.id.bAbokeh);
                        BootFragment.this.startActivity(d);
                }
                });

     return view;



 }}

Boots.java：

package com.cydeon.plasmamodz;

import com.stericson.RootTools.*;
import com.stericson.RootTools.exceptions.RootDeniedException;
import com.stericson.RootTools.execution.CommandCapture;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.net.URL;
import java.net.URLConnection;
import java.util.List;
import java.util.concurrent.TimeoutException;

import com.cydeon.plasmamodz.R;

import android.app.ActionBar;
import android.app.Activity;
import android.app.DownloadManager;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.content.pm.ResolveInfo;
import android.net.Uri;
import android.os.AsyncTask;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import android.widget.Toast;

//Class for Boot Animation Blue Kindle
public class Boots extends Activity {

public static String TAG = "Boots";
Process process;

private class DownloadFile extends AsyncTask<String, Integer, String>{
    @Override
    protected String doInBackground(String... sURL) {
        try{
            URL url = new URL(sURL[0]);
            URLConnection connection = url.openConnection();
            connection.connect();
            //Shows 0-100% progress bar
            int fileLength = connection.getContentLength();

            //Download the file
            InputStream input = new BufferedInputStream(url.openStream());
            OutputStream output = new FileOutputStream("/sdcard/plasma/boot/b..ootanimation.zip");

            byte data[] = new byte[1024];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                total += count;
                //Publish the Progress
                publishProgress((int) (total * 100/fileLength));
                output.write(data, 0, count);
                }

            output.flush();
            output.close();
            input.close();
    } catch (Exception e) {

    }
    return null;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        mProgressDialog.show();
    }

    @Override
    protected void onProgressUpdate(Integer... progress){
        super.onProgressUpdate(progress);
        mProgressDialog.setProgress(progress[0]);



    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        super.onPostExecute(result);
        mProgressDialog.dismiss();
        Context context = getApplicationContext();
        CharSequence text = "Installing. Please Wait";
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(context, text, duration);
        toast.show();

        if (RootTools.isBusyboxAvailable()){
            RootTools.remount("/system", "rw");
            CommandCapture command = new CommandCapture(0, "su", "sh /sdcard/plasma/scripts/boots.sh");
                try {
                    RootTools.getShell(true).add(command).waitForFinish();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } catch (TimeoutException e) {
                    e.printStackTrace();
                } catch (RootDeniedException e) {
                    e.printStackTrace();
                }

        } else {
            RootTools.offerBusyBox(Boots.this);
        }

    }
}

ProgressDialog mProgressDialog;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.boots);
    ActionBar actionBar = getActionBar();
    actionBar.hide();
    ImageView img = (ImageView) findViewById(R.id.iv2);
    img.setImageResource(R.drawable.boot1);
    Button install = (Button) findViewById(R.id.bAInstall);
    Button rtrn = (Button) findViewById(R.id.bAReturn);
    mProgressDialog = new ProgressDialog(Boots.this);
    mProgressDialog.setMessage("Downloading..." );
    mProgressDialog.setIndeterminate(false);
    mProgressDialog.setMax(100);
    mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

    install.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            TextView creator = (TextView) findViewById(R.id.tvCreate);
            Intent bootI = getIntent();
            int dball = getIntent().getExtras().getInt("Dragon", -1);
            int xbox = getIntent().getExtras().getInt("Xbox", -1);
            int GameB = getIntent().getExtras().getInt("GameB", 1);
            if (dball != -1){
            DownloadFile downloadFile = new DownloadFile();
            downloadFile.execute("http:\\correspondingurl");
            creator.setText("Dragon Ball");
            }if (xbox != -1){
                DownloadFile downloadFile = new DownloadFile();
                downloadFile.execute("http:\\correspondingurl");
                creator.setText("Xbox");
            }if (GameB != -1){
                DownloadFile downloadFile = new DownloadFile();
                downloadFile.execute("http:\\correspondingurl");
                creator.setText("GameBoy");
            }


            }

        }
    );

    rtrn.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {
            finish();
        }
    });

    }



}

我尝试了很多不同的方法。这是我最近的尝试。他们都没有工作。

Cat日志：看看顶部...

Answer 1

通过Intent.putExtra（）将所需信息传递给Intent中的新活动（见http://developer.android.com/reference/android/content/Intent.html）

Answer 2

您可以尝试为每个按钮分配一个unique name/id。单击Button时，检索其名称并使用Intent.putExtra()将其传递给新活动。在新活动中，一旦获得此信息，您就可以相应地执行所需的功能。

示例代码：

在按钮的xml中，执行此操作

    android:onClick="OnButtonClick"

在第一个活动的代码中，将OnButtonClick定义为：

   public void OnButtonClick(View v) {
      switch (v.getId()) {
        case R.id.button1:
           doSomething1(); //Intent.putExtra(ButtonID)
            break;
        case R.id.button2:
           doSomething2();
           break;
     }

}

在第二个Activity中，检索此ID并使用类似的switch-case来执行操作，具体取决于Button的ID。

希望这是有道理的！

Answer 3

在您的片段类中，执行以下操作：

public class BootFragment extends Fragment implements android.view.View.OnClickListener{

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,Bundle savedInstanceState) {
        Button Ablue = (Button) view.findViewById(R.id.bABlue);
        Button AblueR = (Button) view.findViewById(R.id.bABlueR);
        Button Abokeh = (Button) view.findViewById(R.id.bAbokeh);

       Ablue.setOnClickListener(this);
       AblueR.setOnClickListener(this);
       Abokeh.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        int btnId = v.getId();
        Intent d = new Intent(getActivity(), Boots.class);
        d.putExtra("BUTTON_ID", btnId);
        startActivity(d);
    }
}

在Boots.java中，执行以下操作：

public class Boots extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {

        int btnId = getIntent().getExtras().getInt("BUTTON_ID", -1);
        switch(btnId){
           case: R.id.your_btn_id_1:
           // logic for your button press
           break;
           case: R.id.your_btn_id_2:
           // logic for your button press
           break;
           case: R.id.your_btn_id_n:
           // logic for your button press
           break;
        }
    }
}

注意：您应该为布局xml文件

中的每个按钮提供唯一ID

Android - 按钮：通过意图/其他方法接收数据

3 个答案: