Question

我目前正在使用android的第一步。我正在开发一个非常简单的计算器，其中我有两个活动，一个主要活动和一个结果活动。在这个结果活动中，我有一个返回按钮，用于主要活动。问题是，当我返回主活动时，文本字段上的值仍然存在。我怎么能这样做，当我从结果活动返回时，主活动上的字段被清除？

以下是我主要活动的代码：

public class MainActivity extends Activity implements OnCheckedChangeListener{

private static final int REQUEST_CODE = 1;
private EditText number1, number2;
private Button btn1;
private Intent intent;
private String operation;
private RadioGroup RadioGroupOperation;

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

    //faz a ligação entre a aplicação e o layout
    number1 = (EditText)findViewById(R.id.editText1);
    number2 = (EditText)findViewById(R.id.editText2);
    btn1 = (Button)findViewById(R.id.calcular);
    intent = new Intent( this, ResultActivity.class);

    btn1.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            //insere na intent os dois numeros digitados pelo utilizador
            intent.putExtra("number1", number1.getText().toString());
            intent.putExtra("number2", number2.getText().toString());
            intent.putExtra("operation", operation);
            startActivityForResult(intent, REQUEST_CODE);
        }
    });
    RadioGroupOperation = (RadioGroup)findViewById(R.id.radioGroup1);
    RadioGroupOperation.setOnCheckedChangeListener(this);
}


@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 void onCheckedChanged(RadioGroup group, int checkedId) {
    switch(checkedId){
    case R.id.soma:
        operation="+";
            break;
    case R.id.subtracao:
        operation="-";
            break;
    case R.id.multiplicacao:
        operation="*";
            break;
    case R.id.divisao:
        operation="/";
            break;
    }
    Toast.makeText(MainActivity.this, operation, Toast.LENGTH_SHORT).show();

}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
    if( resultCode == RESULT_OK && requestCode == REQUEST_CODE ){
        if(data.hasExtra("result")){
            Toast.makeText(this, "O resultado da operação anterior foi:" + data.getExtras().getString("result") , Toast.LENGTH_LONG).show();                
        }
        //testing
        /*if(data.hasExtra("number1") && data.hasExtra("number2")){
            number1.setText(0);
            number2.setText(0);
        }*/
        //end testing

    } 

}

}

我的第二项活动（结果）：

public class ResultActivity extends Activity {

private TextView textView1;
private Intent intent;
private String number1, number2, operation;
private double result;
private Button btn1;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_result);

    btn1 = (Button)findViewById(R.id.voltar);
    intent = getIntent();

    //armazena os numeros digitados
    number1 = intent.getStringExtra("number1");
    number2 = intent.getStringExtra("number2");
    operation = intent.getStringExtra("operation");

    //Efectua calculos
    try {
        if(operation.equals("+"))
            result = (Double.parseDouble(number1) + Double.parseDouble(number2));
        else if(operation.equals("-"))
            result = (Double.parseDouble(number1) - Double.parseDouble(number2));
        else if(operation.equals("*"))
            result = (Double.parseDouble(number1) * Double.parseDouble(number2));
        else if(operation.equals("/"))
            result = (Double.parseDouble(number1) / Double.parseDouble(number2));

        textView1 = (TextView)findViewById(R.id.textView1);
        textView1.setText("O resultado é " + String.valueOf(result));

        btn1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                finish();

            }
            });

        }
        catch(Exception e){
            Toast.makeText(this, "Ocorreu um erro!", Toast.LENGTH_SHORT).show();
            this.finish();
        }       
}

@Override
public void finish(){
Intent data = new Intent();
data.putExtra("result", String.valueOf(result));
//testing
//data.putExtra("number1", 0);
//data.putExtra("number2", 0);
//end testing
setResult(RESULT_OK, data);
super.finish();
}

}

我已经尝试过这样做，如果你看到//测试和//结束测试之间的块，但结果是当我试图回到第一个活动时我崩溃了应用程序。

我对如何做到这一点有任何想法？

提前致谢， CT

Answer 1

在onActivityResult函数内的第一个活动中，您应该重置两个editText

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data){
    if( resultCode == RESULT_OK && requestCode == REQUEST_CODE ){
        if(data.hasExtra("result")){
            Toast.makeText(this, "O resultado da operação anterior foi:" +  data.getExtras().getString("result") , Toast.LENGTH_LONG).show();      
          number1 = (EditText)findViewById(R.id.editText1);
          number2 = (EditText)findViewById(R.id.editText2);          
          number1.setText(0);
          number2.setText(0); 
        }
        //testing
        /*if(data.hasExtra("number1") && data.hasExtra("number2")){
            number1.setText(0);
            number2.setText(0);
        }*/
        //end testing

    } 

}

您的测试代码无法正常工作，因为两个EditText变量未初始化。当你回来时，你在onCreate内进行的inizialization会丢失。

Answer 2

您也可以添加意图来加载您在记事本应用程序上工作的第一个活动：）

btn1.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Intent myIntent = new Intent(getApplicationContext(),MainActiviy.class);
                    startActivity(myIntent);

                             finish();

            }
            });

Answer 3

除了将文本设置为0之外，一切都是正确的.RouitText.setText只接受字符串值。

将测试代码更改为

if(data.hasExtra("number1") && data.hasExtra("number2")){
            number1.setText("0");
            number2.setText("0");
        }

只需要更改setText（“0”）

Android - 重置其他活动的字段

3 个答案: