Question

该应用有两项活动：首先是+ button和listview。当您点击按钮时，使用edittext和ADDbutton打开第二个活动。

单击ADD按钮时，数据写入数据库，然后第二个活动关闭。

那么，当第二项活动关闭时如何制作 - 首次活动刷新中的listview

第一项活动：

public class MainScreen extends FragmentActivity implements OnClickListener {

  final String LOG_TAG = "myLogs";
  ListView listViewMain;
  ImageButton addButton;
  SQLiteDatabase db;
  DataBase DB;
  DBHelper dbHelper;
  Cursor cursor;
  SimpleCursorAdapter passListViewAdapter;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
        setContentView(R.layout.main_screen);

        addButton = (ImageButton) findViewById(R.id.addButton);
        addButton.setOnClickListener(new OnClickListener() {
             public void onClick(View v) {
                 Log.d(LOG_TAG, "add button : ");
                    Intent intentMain = new Intent(MainScreen.this, AddItem.class);
                    startActivity(intentMain);
            }
        });

        DB = new DataBase(this);

        listViewMain = (ListView) findViewById(R.id.listViewMain);

        String[] from = new String[] { DataBase.COLUMN_TITLE,  DataBase.COLUMN_DATE};

        int[] to = new int[] { R.id.titleView, R.id.dateView };
        if (passListViewAdapter == null) {
            passListViewAdapter = new SimpleCursorAdapter(
                    this, 
                    R.layout.item, 
                    DB.fetchAllPass(), 
                    from, 
                    to
                     , SimpleCursorAdapter.FLAG_REGISTER_CONTENT_OBSERVER);
        } else {
            passListViewAdapter.notifyDataSetChanged();            
        }

        listViewMain.setAdapter(passListViewAdapter);


}

@Override
protected void onPause() {
    super.onPause();
}

@Override
protected void onResume() {
    super.onResume();
}

第二个活动（添加行项目）：

 public class AddItem extends MainScreen implements OnClickListener{
     final String LOG_TAG = "myLogs";
     EditText comment_enter, link_enter, password_enter, login_enter, title_enter, date_enter;
     Button add_item_button;
     DBHelper db;
     DataBase DB;
     SimpleCursorAdapter passListViewAdapter;
     SimpleDateFormat sdf;
     private Cursor cursor = null;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.add_item);
    comment_enter = (EditText) findViewById(R.id.comment_enter);
    link_enter = (EditText) findViewById(R.id.link_enter);
    password_enter = (EditText) findViewById(R.id.password_enter);
    login_enter = (EditText) findViewById(R.id.login_enter);
    title_enter = (EditText) findViewById(R.id.title_enter);
    date_enter = (EditText) findViewById(R.id.date_enter);
    SimpleDateFormat sdf = new SimpleDateFormat("dd.MM.yyyy");
    String date = sdf.format(new Date(System.currentTimeMillis()));
    date_enter.setText(date);

    add_item_button = (Button) findViewById(R.id.add_item_button);
    add_item_button.setOnClickListener(new OnClickListener() {
         public void onClick(View v) {
             Log.d(LOG_TAG, "add_item_button : ");
             String title_str = title_enter.getText().toString();
             String login_str = login_enter.getText().toString();
             String pass_str = password_enter.getText().toString();
             String link_str = link_enter.getText().toString();
             String comm_str = comment_enter.getText().toString();

             String date_str = date_enter.getText().toString();

             Log.d(LOG_TAG, "Strings: " + title_str + " " + login_str + " " + pass_str + " " + link_str + " " + comm_str + " " + date_str);
             DataBase DB = new DataBase(AddItem.this);
             DB.open();
             DB.insertPass(title_str, login_str, pass_str, link_str, comm_str, date_str);
             DB.close();
             Log.d(LOG_TAG, "after inserting into DB : ");
             finish();
        }
    });
}

@Override
protected void onPause() {
    super.onPause();
    finish();
    Log.d(LOG_TAG, "onPause : ");
}
}

数据库活动：

public long insertPass (String tt, String lg, String ps, String ul,
    String cm, String dt) {
openGuard();
ContentValues cv = new ContentValues();
cv.put(COLUMN_TITLE, tt);
cv.put(COLUMN_LOGIN, lg);
cv.put(COLUMN_PASSWORD, ps);
cv.put(COLUMN_URL, ul);
cv.put(COLUMN_COMMENT, cm);
cv.put(COLUMN_DATE, dt);

return db.insert(TABLE_NAME, null, cv);}

public Cursor fetchAllPass() throws SQLException {
openGuard();
return db.query(TABLE_NAME, new String[] {COLUMN_ID, COLUMN_TITLE, COLUMN_DATE}, null, null, null, null, null);}

logcat的

02-12 17:24:44.626: D/AndroidRuntime(21123): Shutting down VM
02-12 17:24:44.626: W/dalvikvm(21123): threadid=1: thread exiting with uncaught exception (group=0x415e3c80)
02-12 17:24:44.626: E/AndroidRuntime(21123): FATAL EXCEPTION: main
02-12 17:24:44.626: E/AndroidRuntime(21123): Process: com.ssd.passwordmanager, PID: 21123
02-12 17:24:44.626: E/AndroidRuntime(21123): java.lang.RuntimeException: Unable to resume activity {com.ssd.passwordmanager/com.ssd.passwordmanager.AddItem}: java.lang.NullPointerException
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.ActivityThread.performResumeActivity(ActivityThread.java:2808)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.ActivityThread.handleResumeActivity(ActivityThread.java:2837)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2270)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.ActivityThread.access$800(ActivityThread.java:145)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.os.Handler.dispatchMessage(Handler.java:102)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.os.Looper.loop(Looper.java:136)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.ActivityThread.main(ActivityThread.java:5081)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at java.lang.reflect.Method.invokeNative(Native Method)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at java.lang.reflect.Method.invoke(Method.java:515)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at dalvik.system.NativeStart.main(Native Method)
02-12 17:24:44.626: E/AndroidRuntime(21123): Caused by: java.lang.NullPointerException
02-12 17:24:44.626: E/AndroidRuntime(21123):    at com.ssd.passwordmanager.MainScreen.onResume(MainScreen.java:111)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.Instrumentation.callActivityOnResume(Instrumentation.java:1192)
02-12 17:24:44.626: E/AndroidRuntime(21123):    at android.app.Activity.performResume(Activity.java:5310)

Answer 1

最简单的方法是在第一个活动的onResume中添加加载代码部分。这样每次显示Activity时它都会刷新。

关闭添加行活动后如何刷新listview？

1 个答案: