Java 返回菜单以从webview返回应用程序

我有一个Webview，当我点击actionbar项目时会打开它。 所以我有信用卡和帮助，当我点击后退时，它会关闭应用程序。现在，我希望它不要关闭应用程序，而是回到主屏幕（就像应用程序启动一样） 这是我的主要活动

package com.CPTeam.VselCalc;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.app.SherlockActivity;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;
import com.actionbarsherlock.view.MenuItem;

import crakeron.vsel.calctest.R;



import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.webkit.WebView;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.Toast;

    public class VselcalculatortestActivity extends SherlockActivity {
private EditText freqbox1;
private EditText freqbox2;
private EditText freqbox3;
private EditText freqbox4;
private EditText freqbox5;
private EditText voltbox1;
private EditText voltbox2;
private EditText voltbox3;
private EditText voltbox4;
private EditText voltbox5;
private Spinner spinner;

public int freq1;
public int freq2;
public int freq3;
public int freq4;
public int freq5;
public int volt1;
public int volt2;
public int volt3;
public int volt4;
public int volt5;

public boolean stop=false;
public boolean freq4ornot=false;
public boolean freq5ornot=false;

//public String path;

/** Called when the activity is first created. */

private AutoUpdateApk aua;  
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    aua = new AutoUpdateApk(getApplicationContext()); 

    ActionBar actionBar = getSupportActionBar();
    //could be used to modify actionbar if needed





    ChangeLog cl = new ChangeLog(this);
    if (cl.firstRun())
        cl.getLogDialog().show();

    //cl.getFullLogDialog().show(); for testing 

    freqbox1 = (EditText) findViewById(R.id.freq1);
    freqbox2 = (EditText) findViewById(R.id.freq2);
    freqbox3 = (EditText) findViewById(R.id.freq3);
    freqbox4 = (EditText) findViewById(R.id.freq4);
    freqbox5 = (EditText) findViewById(R.id.freq5);
    voltbox1 = (EditText) findViewById(R.id.volt1);
    voltbox2 = (EditText) findViewById(R.id.volt2);
    voltbox3 = (EditText) findViewById(R.id.volt3);
    voltbox4 = (EditText) findViewById(R.id.volt4);
    voltbox5 = (EditText) findViewById(R.id.volt5);

    spinner = (Spinner) findViewById(R.id.spinner1);
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this,
    R.array.spinner_choices, android.R.layout.simple_spinner_item);
    // Specify the layout to use when the list of choices appears
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    // Apply the adapter to the spinner
    spinner.setAdapter(adapter);

    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener(){
                public void onItemSelected(AdapterView <?> adapter, View v, int pos, long lng) {
                    if (pos==0){
                        freq4ornot=false;
                        freq5ornot=false;
                        hide_row4();
                        hide_row5();
                        }
                    if (pos==1){
                        freq4ornot=true;
                        freq5ornot=false;
                        show_row4();
                        hide_row5();
                        }   
                    if (pos==2){
                        freq4ornot=true;
                        freq5ornot=true;
                        show_row4();
                        show_row5();
                        }
                }

                public void onNothingSelected(AdapterView <?> arg0) {
                    //nothing FTM
                }
    });
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater = getSupportMenuInflater();
    inflater.inflate(R.menu.menu, menu);   
    return true;
}



public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case R.id.Changelog:
        new ChangeLog(this).getFullLogDialog().show();;
        return true;

    case R.id.Help:
        WebView webview = new WebView(this);
         setContentView(webview);
         webview.loadUrl("file:///android_res/raw/help.html");  
    return true;

    case R.id.Credits:
        WebView webview1 = new WebView(this);
     setContentView(webview1);
    webview1.loadUrl("file:///android_res/raw/credits.html"); 
        return true;


    }
    return true;
}






public void show_row4(){
    freqbox4.setVisibility(View.VISIBLE);
    findViewById(R.id.textView8).setVisibility(View.VISIBLE);
    findViewById(R.id.TextView03).setVisibility(View.VISIBLE);
    voltbox4.setVisibility(View.VISIBLE);
    Log.d("VselCalc", "Showing row 4");

}

public void hide_row4(){
    freqbox4.setVisibility(View.INVISIBLE);
    findViewById(R.id.textView8).setVisibility(View.INVISIBLE);
    findViewById(R.id.TextView03).setVisibility(View.INVISIBLE);
    voltbox4.setVisibility(View.INVISIBLE);
    Log.d("VselCalc", "Hiding row 4");
}
public void show_row5(){
    freqbox5.setVisibility(View.VISIBLE);
    findViewById(R.id.textView9).setVisibility(View.VISIBLE);
    findViewById(R.id.TextView04).setVisibility(View.VISIBLE);
    voltbox5.setVisibility(View.VISIBLE);
    Log.d("VselCalc", "Showing row 5");

}

public void hide_row5(){
    freqbox5.setVisibility(View.INVISIBLE);
    findViewById(R.id.textView9).setVisibility(View.INVISIBLE);
    findViewById(R.id.TextView04).setVisibility(View.INVISIBLE);
    voltbox5.setVisibility(View.INVISIBLE);
    Log.d("VselCalc", "Hiding row 5");
}

public void button_pressed(View button) { 
    voltbox1.setText("");
    voltbox2.setText("");
    voltbox3.setText("");
    voltbox4.setText("");
    voltbox5.setText("");
    stop=false;
    // 1. Grab values in textboxes freq1,2,3 (and 4 and 5, depending on Spinner value?) and store their values
    grab_values(freq4ornot, freq5ornot);
    // 2. Call calculate function with 3 (or 5) arguments
    calculate(freq1, freq2, freq3, freq4, freq4ornot, freq5ornot);
    // 3. call function to display each result in correct box, if stop=true, then all boxes will be displayed empty
    display_volt(freq4ornot, freq5ornot);
    if(stop==true) error_empty();
}

public void grab_values(boolean freq4ornot, boolean freq5ornot){
    String freq1Value = freqbox1.getText().toString();//fetch what's in edittextbox and store it in a string
    if(freq1Value.length()!=0){
        freq1 = Integer.parseInt(freq1Value);//transform the string into an int and store it in our variable
        }
    if(freq1Value.length()==0){
        stop=true;
        freq1=0;
        }

    String freq2Value = freqbox2.getText().toString();
    if(freq2Value.length()!=0){
        freq2 = Integer.parseInt(freq2Value);//transform the string into an int and store it in our variable
        }
        if(freq2Value.length()==0){//check if user entered a value in box, otherwise causes crash
        stop=true;                      
        freq2=0;
        }

    String freq3Value = freqbox3.getText().toString();
    if(freq3Value.length()!=0){
        freq3 = Integer.parseInt(freq3Value);
        }
        if(freq3Value.length()==0){
            stop=true;                      
            freq3=0;
        }

    if (freq4ornot==true){
        String freq4Value = freqbox4.getText().toString();
        if(freq4Value.length()!=0){
            freq4 = Integer.parseInt(freq4Value);
            }
            if(freq4Value.length()==0){
                stop=true;                                  
                freq4=0;
            }
    if (freq5ornot==true){
        String freq5Value = freqbox5.getText().toString();
        if(freq5Value.length()!=0){
            freq5 = Integer.parseInt(freq5Value);
            }
            if(freq5Value.length()==0){
                stop=true;                                  
                freq5=0;
            }

    }}

}

public void calculate(int freq1,int freq2, int freq3, int freq4, boolean freq4ornot, boolean freq5ornot){
    volt1 = formula(freq1);
    volt2 = formula(freq2);
    volt3 = formula(freq3);
    if (freq4ornot==true){volt4 = formula(freq4);}
    if (freq5ornot==true){volt5 = formula(freq5);}
}


public int formula(int freq){
    int volt = ((freq/20)+2);
    return volt;
}


public void display_volt (boolean freq4ornot,boolean freq5ornot){
    if(stop==false){
        voltbox1.setText(String.valueOf(volt1));
        voltbox2.setText(String.valueOf(volt2));
        voltbox3.setText(String.valueOf(volt3));
        if(freq4ornot==true){voltbox4.setText(String.valueOf(volt4));}
        if(freq5ornot==true){voltbox5.setText(String.valueOf(volt5));}
    }

}


public void error_empty(){
    Toast.makeText(getApplicationContext(), "Please enter a frequency in all the boxes", Toast.LENGTH_LONG).show();
    /* For debug purposes
    Toast.makeText(getApplicationContext(),"stop bool is " + stop, Toast.LENGTH_LONG).show();*/
}








                    //AUTODETECTION FUNCTIONS!!!

private int detected_freq1;
private int detected_freq2;
private int detected_freq3;
private int detected_freq4;
private int detected_freq5;
private String path;

public void auto_detect(View button){
    stop=false;
    freq4ornot=false;
    freq5ornot=false;
    //get the path string (for multiple device support) that leads to the cpu_freq file
        {get_path();}       
    //read and process the file specified by path() and extract the frequencies         
        detect();       
    //fill the 4/5 freq boxes with the frequencies found
        write_freq(detected_freq1,detected_freq2,detected_freq3,detected_freq4,detected_freq5);

        if (stop==true){error_device();}
    }

    private void get_path(){
        //find path for frequencies available
        // for Defy (and milestone, and many other android devices) it is /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
        // for multiple devices support, probably store the paths in a table in the future          
        path="/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies";

        //for testing, put a file called "Test" in the root directory of your phone to test behavior on 4/5 freqs
        //path="/Test";
    }

    private void detect(){
        String[] segs;
        FileReader fstream;
        long Read;

        try {fstream = new FileReader(path);
        Log.d("VselCalc_AutoD", "Opened '" + path + "' file correctly");
        } 
        catch (FileNotFoundException e) {               
            Toast.makeText(getApplicationContext(), "Could not read " + path, Toast.LENGTH_LONG).show();
            stop=true;
            return;
        }

        BufferedReader in = new BufferedReader(fstream, 500);
        String line;
        try {
            while ((line = in.readLine()) != null) {

                    Log.d("VselCalc_AutoD", "line read:"+  line);
                    segs = line.trim().split(" ");
                    Log.d("VselCalc_AutoD", "segs length: " + segs.length);

                    Read = Long.parseLong(segs[0]);
                    Log.d("VselCalc_AutoD", "Auto-Detect freq. Read1: " + Read);  
                    detected_freq1= (int) Read/1000;

                    Read = Long.parseLong(segs[1]);
                    Log.d("VselCalc_AutoD", "Auto-Detect freq. Read2: " + Read);
                    detected_freq2= (int) Read/1000;

                    Read = Long.parseLong(segs[2]);
                    Log.d("VselCalc_AutoD", "Auto-Detect freq. Read3: " + Read);
                    detected_freq3= (int) Read/1000;

                    hide_row4();
                    hide_row5();
                    spinner.setSelection(0);

                    if(segs.length>=4){
                    Read = Long.parseLong(segs[3]);
                    Log.d("VselCalc_AutoD", "Freq4 exists. Auto-Detect freq. Read4: " + Read);
                    detected_freq4= (int) Read/1000;
                    freq4ornot=true;
                    spinner.setSelection(1);
                    Log.d("VselCalc_AutoD", "freq4ornot changed to true after auto-detect");
                    Log.d("VselCalc_AutoD", "freq5 or not: " + freq5ornot);
                    show_row4();
                    hide_row5();
                    }

                    if(segs.length>=5){
                    Read = Long.parseLong(segs[4]);
                    Log.d("VselCalc_AutoD", "Freq5 exists. Auto-Detect freq. Read5: " + Read);
                    detected_freq5= (int) Read/1000;
                    freq5ornot=true;
                    spinner.setSelection(2);
                    Log.d("VselCalc_AutoD", "freq5ornot changed to true after auto-detect");
                    show_row4();
                    show_row5();
                    }


            }               
        } catch (IOException e) {
            Log.e("readfile", e.toString());
        }
        return ;
    }                       

    public void write_freq(int fr1, int fr2, int fr3, int fr4, int fr5 ){
        if(stop==false){
            freqbox1.setText(String.valueOf(fr1));
            freqbox2.setText(String.valueOf(fr2));
            freqbox3.setText(String.valueOf(fr3));
            if(freq4ornot==true){freqbox4.setText(String.valueOf(fr4));}
            if(freq5ornot==true){freqbox5.setText(String.valueOf(fr5));}
            Toast.makeText(getApplicationContext(), "Auto-Detection successful!", Toast.LENGTH_LONG).show();
        }           
    }

    public void error_device(){
        Toast.makeText(getApplicationContext(), "Function may not be supported on your device. Please contact the developers", Toast.LENGTH_LONG).show();
    }

---

目标Android版本是4.1

您应该在活动类中重写

onBackPressed（）

public void onBackPressed ()

自：当活动检测到用户的 按后退键。默认实现只是完成 当前活动，但您可以覆盖此活动以执行任何您想要的操作

在活动中复制此代码，并在其中执行任何操作

@Override
    public void onBackPressed() {
        // TODO Auto-generated method stub
            //this is where you start your activity
    }

---

按下后退按钮时，当前意图/活动关闭并返回到堆栈中的上一个意图/活动。这里您正在创建一个webview，并将其设置为当前活动的内容。因此，当您按back键时，活动将关闭，这反过来又会关闭应用程序，因为您之前没有任何意图/活动。取而代之的是重写onBackPressed，并在其中设置ContentView作为主布局

@Override
    public void onBackPressed() {
        // TODO Auto-generated method stub
            setContentView(R.layout.main);
            //Do other functions you want to do here  
    }

---

怎么用？写什么？你能说得更详细一点吗？我以前做过。但我想回到应用程序。不要关闭它。我尝试了各种解决方案，但总是得到了FC！我用一段代码编辑了我的webview所在的问题。“默认后退按钮关闭当前活动。”当您覆盖此方法时，后退按钮将不再关闭您的应用程序。它会像你在这个方法中写的那样反应。是的..但是我希望它进入默认菜单（当我启动应用程序时），而不是停留在WebView中。我会更清楚：如果你想用backpress启动一个活动，你必须用OnBackpress（）方法写它。在这个方法中写“startActivity（your Intent）”。我已经这么做了，但我无法在主菜单中退出应用程序。它会继续重新启动活动。你想重新启动活动或返回上一页（R.layout.main），你想要什么？我想返回R.layout.main，但只能从这两个webivews返回。我的应用程序不全是webview。它有很多按钮、微调器菜单。我添加了webview以获得帮助和信任。我会告诉你一个简单的解决方案。当这两个Web视图被加载/设置为“活动”的内容时，将标志设为true。并在背面按下，检查该标志是否正确。如果标志为true，则使用setcontentview（R.layout.main）else super.onBackPressed（）；将该标志声明为全局标志

@Override
    public void onBackPressed() {
        // TODO Auto-generated method stub
            setContentView(R.layout.main);
            //Do other functions you want to do here  
    }