用户在另一个 class 中输入后在 TextView 中显示字符串

Question

我正在尝试将字符串从 class (UserInput) 传递到 Main Activity 并将其显示在 TextView 中。用户应该按下 Main Activity 中的一个按钮，它调用 UserInput 并输入一个字符串。使用共享首选项，我设法传递了字符串，但无法在 TextView 中显示它。

我意识到getSharedPreference 和setText 部分是在class 开始之前完成的，导致从UserInput 返回后TextView 没有更新，我不知道如何解决这个问题。任何帮助都感激不尽。谢谢！

主要Activity代码

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

TextView tvCode;
Button btnCode, btnClear;
TextInputLayout textInputMessage;
String preferenceFileName, preferenceKey, retreivedCodeString;

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

    tvCode = findViewById(R.id.textViewCode);
    btnCode = findViewById(R.id.buttonCode);
    btnClear = findViewById(R.id.buttonClear);
    textInputMessage = findViewById(R.id.textInputLayoutMessage);
    preferenceFileName = "PreferenceFile";
    preferenceKey = "CodeKey";


    SharedPreferences sharedPreferences = getSharedPreferences(preferenceFileName, MODE_PRIVATE);
    retreivedCodeString = sharedPreferences.getString(preferenceKey,"");
    tvCode.setText(retreivedCodeString);

    btnCode.setOnClickListener(this);
    btnClear.setOnClickListener(this);
}


@Override
public void onClick(View arg0) {
    switch (arg0.getId()){
        case R.id.buttonClear:
            //method
            break;
        case R.id.buttonCode:
            Intent intent = new Intent(this, UserInput.class);
            startActivity(intent);
            sharedPreferences = getSharedPreferences(preferenceFileName, MODE_PRIVATE);
            retreivedCodeString = sharedPreferences.getString(preferenceKey,"");
            tvCode.setText(retreivedCodeString);
            break;
    }

}

用户输入代码

public class UserInput extends Activity implements View.OnClickListener {
String userInputCode, preferenceFileName, preferenceKey;
TextInputLayout subTextInputLayoutCode;

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

    subTextInputLayoutCode = findViewById(R.id.textInputLayoutCode);
    Button btnOk = findViewById(R.id.buttonOk);
    Button btnCancel = findViewById(R.id.buttonCancel);
    preferenceFileName = "PreferenceFile";
    preferenceKey = "CodeKey";

    btnOk.setOnClickListener(this);
    btnCancel.setOnClickListener(this);
}

@Override
public void onClick(View arg0) {
    switch (arg0.getId()){
        case R.id.buttonOk:
            if (!validateCode()){
                return;
            }
            userInputCode = subTextInputLayoutCode.getEditText().getText().toString();
            SharedPreferences sharedPreferences = getSharedPreferences(preferenceFileName, MODE_PRIVATE);
            SharedPreferences.Editor editor = sharedPreferences.edit();
            editor.putString(preferenceKey,userInputCode);
            editor.apply();
            finish();
            break;
        case R.id.buttonCancel:
            finish();
            break;
    }
}

Answer 1

方式一：

在 MainActivity

的 onResume 方法中使用以下代码

SharedPreferences sharedPreferences = getSharedPreferences(preferenceFileName, MODE_PRIVATE);
retreivedCodeString = sharedPreferences.getString(preferenceKey,"");
tvCode.setText(retreivedCodeString);

方式二：

开始你的 UserInput activity 结果 (startActivitForResult(intent, 123))

并使用下面的代码

完成你的UserInput activity

setResult(Activity.RESULT_OK)
finish()

在您的主要 activity 覆盖 onActivityResultMethode 如下所示

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    if(requestCode == 123 && resultCode == Activity.RESULT_OK){
         SharedPreferences sharedPreferences = getSharedPreferences(preferenceFileName, MODE_PRIVATE);
         retreivedCodeString = sharedPreferences.getString(preferenceKey,"");
         tvCode.setText(retreivedCodeString);
    } else {
        super.onActivityResult(requestCode, resultCode, data)
    }
}

方式 3：（无 sharedPreferences）

开始你的 UserInput activity 结果 (startActivitForResult(intent, 123))

并使用下面的代码

完成你的UserInput activity

Intent i = new Intent();
Bundle b = new Bundle();
b.putString("inputText", YOUR_INPUT_TEXT);
i.putExtras(b);
setResult(123, i)
finish()

在您的主要 activity 覆盖 onActivityResultMethode 如下所示

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
    if(requestCode == 123 && resultCode == Activity.RESULT_OK){
         tvCode.setText(data.getExtras().getString("inputText",""));
    } else {
        super.onActivityResult(requestCode, resultCode, data)
    }
}