SharedPreferences无法在活动中使用

Posted 2021-04-14

我正在尝试在活动中获取SharedPreferences并将值设置为操作栏的标题，但我无法获取main_activity的值，但我可以在另一个中获取值，我不知道为什么以及如何。这是我保存SharedPreferences的代码：

public static final String Colloge_section="MyPrefsFile";
SharedPreferences.Editor 
editor=getSharedPreferences(Colloge_section,MODE_PRIVATE).edit();
        editor.putString("title_of_activity","student");
        editor.apply();

这就是我获得SharedPreferences的方式：

SharedPreferences prfs = getSharedPreferences("MyPrefsFile", Context.MODE_PRIVATE);
    String Astatus = prfs.getString("title_of_activity", "");

    getSupportActionBar().setTitle(Astatus);

这是我的主要活动：

public class KworldActivity extends AppCompatActivity
    implements NavigationView.OnNavigationItemSelectedListener {
NavigationView navigationView=null;
Toolbar toolbar=null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_kworld);
    //set the fragment initialty
    boolean net=isNetworkConnected();
    if (net==true)
    {
        RssMainFragment fragment=new RssMainFragment();
        android.support.v4.app.FragmentTransaction fragmentTransaction=getSupportFragmentManager().beginTransaction();
        fragmentTransaction.replace(R.id.fragment_container,fragment);
        fragmentTransaction.commit();
    }else {
        Toast.makeText(KworldActivity.this, "انت غير متصل بالانترنت الرجاء المحاوله لاحقا", Toast.LENGTH_LONG).show();
    }

    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    SharedPreferences prfs = getSharedPreferences("MyPrefsFile", Context.MODE_PRIVATE);
    String Astatus = prfs.getString("titleofactivity", "");

    getSupportActionBar().setTitle(Astatus);

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
            this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
    drawer.addDrawerListener(toggle);
    toggle.syncState();

    navigationView = (NavigationView) findViewById(R.id.nav_view);
    navigationView.setNavigationItemSelectedListener(this);
}
private boolean isNetworkConnected() {
    ConnectivityManager cm = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);

    return cm.getActiveNetworkInfo() != null;
}
@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.kworld, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    if (id == R.id.action_about ) {
        Intent homeIntent=new Intent(KworldActivity.this,AboutActivity.class);
        startActivity(homeIntent);
        finish();
        //return true;
    }else if(id == R.id.action_develop ) {
        Intent homeIntent=new Intent(KworldActivity.this,DevelopActivity.class);
        startActivity(homeIntent);
        finish();
        //return true;
    }else if(id == R.id.action_share ) {
        //Share Code is here
        ApplicationInfo app = getApplicationContext().getApplicationInfo();
        String filePath = app.sourceDir;

        Intent intent = new Intent(Intent.ACTION_SEND);

        // MIME of .apk is "application/vnd.android.package-archive".
        // but Bluetooth does not accept this. Let's use "*/*" instead.
        intent.setType("*/*");

        // Append file and send Intent
        File originalApk = new File(filePath);

        try {
            //Make new directory in new location
            File tempFile = new File(getExternalCacheDir() + "/ExtractedApk");
            //If directory doesn't exists create new
            if (!tempFile.isDirectory())
                if (!tempFile.mkdirs())
                    return true;
            //Get application's name and convert to lowercase
            tempFile = new File(tempFile.getPath() + "/" + getString(app.labelRes).replace(" ","").toLowerCase() + ".apk");
            //If file doesn't exists create new
            if (!tempFile.exists()) {
                if (!tempFile.createNewFile()) {
                    return true;
                }
            }
            //Copy file to new location
            InputStream in = new FileInputStream(originalApk);
            OutputStream out = new FileOutputStream(tempFile);

            byte[] buf = new byte[1024];
            int len;
            while ((len = in.read(buf)) > 0) {
                out.write(buf, 0, len);
            }
            in.close();
            out.close();
            System.out.println("File copied.");
            //Open share dialog
            intent.putExtra(Intent.EXTRA_STREAM, Uri.fromFile(tempFile));
            startActivity(Intent.createChooser(intent, "Share app via"));

        } catch (IOException e) {
            e.printStackTrace();
        }
        //return true;
    }else if(id == R.id.action_state ) {
        buadd();
        //return true;
    }

    return super.onOptionsItemSelected(item);
}
public void buadd(){
    SharedPreferences prfs = getSharedPreferences("MyPrefsFile", Context.MODE_PRIVATE);
    final String Std_id = prfs.getString("std_name", "");
    Thread runt=new Thread(){
        public void run(){
            CallLibViewer cweb=new CallLibViewer();
            cweb.OpenPhotoCopyViewer(Std_id);}
    };
    runt.start();
    try{
        runt.join();
        Toast t1 =Toast.makeText(this, ContactResult.CopyViewerMessage,Toast.LENGTH_LONG);
        View t2=t1.getView();
        t2.setBackgroundColor(Color.BLACK);
        t1.show();
    }
    catch(Exception ex){
    }
}
private void displaySelectedScreen(int itemId) {

    //creating fragment object
    Fragment fragment = null;
    SharedPreferences prfs = getSharedPreferences("MyPrefsFile", Context.MODE_PRIVATE);
    String Astatus = prfs.getString("titleofactivity", "");
    //initializing the fragment object which is selected
    switch (itemId) {
        case R.id.nav_news:
            fragment = new RssMainFragment();
            getSupportActionBar().setTitle(Astatus);
            break;
        case R.id.nav_lib:
            fragment = new LibraryFragment();
            getSupportActionBar().setTitle("المكـتبة");
            break;
        case R.id.nav_notify:
            fragment = new NotificationFragment();
            getSupportActionBar().setTitle("لوحة الاشعارات");
            break;
        case R.id.nav_manage:
            fragment = new OtherFragment();
            getSupportActionBar().setTitle("خدمـات اخرى");
            break;
        case R.id.nav_contact:
            fragment = new ContactFragment();
            getSupportActionBar().setTitle("تواصل معنا");
            break;
        case R.id.nav_setting:
            Intent homeIntent=new Intent(KworldActivity.this,SettingsActivity.class);
            startActivity(homeIntent);
            finish();
            break;
    }

    //replacing the fragment
    if (fragment != null) {
        FragmentManager manager = getSupportFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.replace(R.id.fragment_container, fragment);
        transaction.commit();

    }

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
}

@SuppressWarnings("StatementWithEmptyBody")
@Override
public boolean onNavigationItemSelected(MenuItem item) {

    //calling the method displayselectedscreen and passing the id of selected menu
    displaySelectedScreen(item.getItemId());
    //make this method blank
    return true;
}

}

答案

试试这段代码：

SharedPreferences sharedPreferencesObj=getApplicationContext().getSharedPreferences("MyPrefsFile", MODE_PRIVATE);


SharedPreferences.Editor editor = sharedPreferencesObj.edit();
                    editor.putString("title_of_activity","student");  
                    editor.commit();

String title=sharedPreferencesObj.getString("title_of_activity", "")

另一答案

对SharedPreferences使用以下代码来保存数据

SharedPreferences prefs = context.getSharedPreferences("PrefName", context.MODE_PRIVATE);
    SharedPreferences.Editor editor = prefs.edit();
    editor.putString("Token", "tokenValue");
    editor.apply();

用于获取数据

SharedPreferences preferences = context.getSharedPreferences("PrefName", context.MODE_PRIVATE);
        String SavedToken= preferences.getString("Token", null);