java - 如何在 Android Studio 中从 Onclick() 获取字符串值到 onSaveInstanceState()

Question

public class MainActivity extends AppCompatActivity implements View.OnClickListener
{
    Button buttonshow;
    EditText edittextname;
    TextView textviewshow;
    String etText;

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

        buttonshow = findViewById(R.id.buttonShow);
        edittextname = findViewById(R.id.editTextName);
        textviewshow = findViewById(R.id.textViewShow);

        buttonshow.setOnClickListener(this);
    }

    @Override
    public void onClick(View v)
    {

        etText = edittextname.getText().toString();
        if (v.getId() == R.id.buttonShow)
        {
            textviewshow.setText(etText);
        }
    }

    @Override
    protected void onSaveInstanceState(@NonNull Bundle outState)
    {
        super.onSaveInstanceState(outState);
        outState.putString("textname", etText);
    }

    @Override
    protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState)
    {
        super.onRestoreInstanceState(savedInstanceState);
        etText = savedInstanceState.getString("textname");
    }
}

我正在学习使用 onSaveInstanceState()和 onRestoreInstanceState() .所以当我的 Activity 变成风景时，我可以恢复字符串。但我无法从 Onclick() 获得值(value)到其他方法。我需要 etText 的字符串值至 onSaveInstanceState()和 onRestoreInstanceState() .否则，这些方法不起作用。当 Activity 变为横向时，我无法恢复此字符串值。

Answer 1

像这样做:

public class MainActivity extends AppCompatActivity
{
    private final String TEXT_KEY = "TEXT_KEY";
    Button buttonshow;
    EditText edittextname;
    TextView textviewshow;
    String etText;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("MyTag", "onCreate");

        buttonshow = findViewById(R.id.buttonShow);
        edittextname = findViewById(R.id.editTextName);
        textviewshow = findViewById(R.id.textViewShow);

        buttonshow.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                etText = edittextname.getText().toString();
                textviewshow.setText(etText);
            }
        });
    }

    @Override
    protected void onSaveInstanceState(@NonNull Bundle outState)
    {
        super.onSaveInstanceState(outState);
        Log.d("MyTag", "onSaveInstanceState");
        outState.putString(TEXT_KEY, etText);
    }

    @Override
    protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState)
    {
        super.onRestoreInstanceState(savedInstanceState);
        Log.d("MyTag", "onRestoreInstanceState");
        etText = savedInstanceState.getString(TEXT_KEY);
        textviewshow.setText(etText);
    }
}

当您恢复变量时，您必须将其设置为 View 。

你也不需要 ettext变量，以便更清楚你可以这样做(我没有实现 OnClickListenner 并在代码中设置它，我认为这是一种更好的方法):

public class MainActivity extends AppCompatActivity
{
    private final String TEXT_KEY = "TEXT_KEY";
    Button buttonshow;
    EditText edittextname;
    TextView textviewshow;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Log.d("MyTag", "onCreate");

        buttonshow = findViewById(R.id.buttonShow);
        edittextname = findViewById(R.id.editTextName);
        textviewshow = findViewById(R.id.textViewShow);

        buttonshow.setOnClickListener(new View.OnClickListener()
        {
            @Override
            public void onClick(View view)
            {
                textviewshow.setText(edittextname.getText().toString());
            }
        });
    }

    @Override
    protected void onSaveInstanceState(@NonNull Bundle outState)
    {
        super.onSaveInstanceState(outState);
        Log.d("MyTag", "onSaveInstanceState");
        outState.putString(TEXT_KEY, textviewshow.getText().toString());
    }

    @Override
    protected void onRestoreInstanceState(@NonNull Bundle savedInstanceState)
    {
        super.onRestoreInstanceState(savedInstanceState);
        Log.d("MyTag", "onRestoreInstanceState");
        textviewshow.setText(savedInstanceState.getString(TEXT_KEY));
    }
}