Question

我有两个活动MainActivity和MenuActivity。我需要将Menu Activity中的ArrayList传递给Main Activity。我是用意图做的。

MenuActivity.java

    public class MenuActivity extends ActionBarActivity {

    Button add,save;
     EditText subject;
     ArrayList list = new ArrayList();
     protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.subject_main);
     add = (Button) findViewById(R.id.button1);
     subject = (EditText) findViewById(R.id.editText1);
     save= (Button) findViewById(R.id.button2);




     add.setOnClickListener(new OnClickListener() {


         Context context;

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String content;
             content = subject.getText().toString();

             MainActivity.myStringList.add(content);
            ArrayAdapter dataAdapter = new ArrayAdapter(MenuActivity.this,android.R.layout.simple_spinner_item, list);

            dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);

              //spinner1.setAdapter(dataAdapter);
             // Showing selected spinner item
                   Toast.makeText(getApplicationContext(),
                            content +"Added", Toast.LENGTH_LONG).show();


        }
       });
     save.setOnClickListener(new OnClickListener() {


         Context context;

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub

            Intent i1 = new Intent(MenuActivity.this, MainActivity.class);
            i1.putStringArrayListExtra("LIST",list);

             startActivity(i1);


        }
       });



}
}

Arraylist列表需要在MainActivity中使用

MainActivity.java

public class MainActivity extends ActionBarActivity {
 Spinner spinner1,spinner2,spinner3;
 public static List myStringList = new ArrayList();


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    if(myStringList.isEmpty())
    {
        Intent myIntent = new Intent(MainActivity.this, MenuActivity.class);

        MainActivity.this.startActivity(myIntent);

    }
 // Spinner element
   spinner1 = (Spinner) findViewById(R.id.spinner1);
   spinner2 = (Spinner) findViewById(R.id.spinner2);
   spinner3 = (Spinner) findViewById(R.id.spinner3);





    ArrayAdapter dataAdapter = new ArrayAdapter(MainActivity.this,android.R.layout.simple_spinner_item, myStringList);

    dataAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    spinner1.setAdapter(dataAdapter);


// Spinner click listener

   //spinner2.setOnItemSelectedListener(this);
   //spinner3.setOnItemSelectedListener(this);
   spinner1.setOnItemSelectedListener(new OnItemSelectedListener() {

       @Override
       public void onItemSelected(AdapterView<?> adapter, View v,
               int position, long id) {
           // On selecting a spinner item
           String item = adapter.getItemAtPosition(position).toString();

       }   

       @Override
       public void onNothingSelected(AdapterView<?> arg0) {
           // TODO Auto-generated method stub

       }
   });


    }
public void addListenerOnSpinnerItemSelection() {
    spinner1 = (Spinner) findViewById(R.id.spinner1);
    spinner1.setOnItemSelectedListener(new OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2,
            long arg3) {
            //do something here
        }
        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
            //optionally do something here
        }
    });
  }



@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.




    getMenuInflater().inflate(R.menu.main, 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.


        switch (item.getItemId())
        {
        case R.id.settings:
            // Single menu item is selected do something
            // Ex: launching new activity/screen or show alert message

            return true;

        case R.id.help:

            return true;

        case R.id.subjects:
            Intent myIntent = new Intent(MainActivity.this, MenuActivity.class);

            MainActivity.this.startActivity(myIntent);

            return true;


        default:
            return super.onOptionsItemSelected(item);
        }
    }

如何在MainActivty中显示ArrayList？

Answer 1

MainActivity是您启动应用时发生的第一项活动吗？如果是，当onCreate第一次运行时，将不会填充list1。我假设您的MainActivity在某个时刻调用了MenuActivity，然后您的MenuActivity通过使用intent返回MainActivity，此时MainActivity会更新spinners？您可以尝试的其他内容是在MainActivity的onCreate之前输入：

public static List<String> myStringList = new ArrayList<String>();

当您添加到MenuActivity中的列表时，请使用MainActivity.myStringList.add(content);

然后，当您完成添加到MenuActivity中的列表时，您可以调用finish();返回MainActivity，您可以通过覆盖onResume方法来更新微调器。示例 - 在onCreate方法下面的MainActivity中：

@Override
public void onResume(){
    super.onResume();
    try{
        spinner1 = (Spinner) findViewById(R.id.spinner1);
        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, myStringList.toArray(), android.R.layout.simple_spinner_item);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner1.setAdapter(adapter);
    } catch (RuntimeException e){
        Log.d("error",e+"");
    }
}

这是来自记忆，所以如果它有一些问题我很抱歉。 runtimexception是这样的，它不会在第一次调用onResume时崩溃（在初始化其他任何东西之前）。

当我使用intent从另一个活动中检索数据时，应用程序崩溃

1 个答案: