我想实现,比方说温度单位转换器。我想使用android MVVM和数据绑定来执行此操作,但我不知道如何操作。我有一个包含三个EditText字段的片段:摄氏,华氏度,开尔文。更改其中之一后,其余的应自动更新。没有数据绑定,我将TextWatcher设置为每个字段,并在onTextChanged中执行所有验证和转换逻辑并设置其他字段的值。在beforeTextChanged中,我删除了对其他字段的侦听器,在afterTextChanged中,再次设置了它们,以避免在更新一个字段时出现无限循环,并触发TextWatcher来更新另一个字段,依此类推...
这是没有数据绑定的简化代码。
celsiusEditTextWatcher = new TextWatcher() {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
fahrenheitEditText.removeTextChangedListener(fahrenheitEditTextWatcher);
kelvinEditText.removeTextChangedListener(kelvinEditTextWatcher);
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
double celsius = String.valueOf(celsiusEditText.getText());
double fahrenheit = celsiusToFahrenheit(celsius);
double kelvin = celsiusToKelvin(celsius)
fahrenheitEditText.setText(Double.toString(fahrenheit));
kelvinEditText.setText(Double.toString(kelvin));
}
@Override
public void afterTextChanged(Editable s) {
fahrenheitEditText.addTextChangedListener(fahrenheitEditTextWatcher);
kelvinEditText.addTextChangedListener(kelvinEditTextWatcher);
}
};
感谢任何帮助。
我提出了一个非常简单的解决方案。在这里,让A和B是EditText,当用户通过用户输入更改文本时,需要同步这些EditText。同时,它们各自对应的LiveData也将更新:
package marabillas.loremar.edittextmvvm;
import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
public class MainActivity extends AppCompatActivity {
private AViewModel viewModel;
private AListener aListener = new AListener();
private BListener bListener = new BListener();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final EditText a = findViewById(R.id.aEdit);
final EditText b = findViewById(R.id.bEdit);
viewModel =
new ViewModelProvider(getViewModelStore(), new ViewModelProvider.NewInstanceFactory()).get(AViewModel.class);
a.addTextChangedListener(aListener);
b.addTextChangedListener(bListener);
viewModel.isFieldsSynced = false;
viewModel.aEditData.observe(this, new Observer<String>() {
@Override
public void onChanged(String s) {
if (!a.getText().toString().equals(s)) {
a.setText(s);
}
if (viewModel.isFieldsSynced) {
viewModel.isFieldsSynced = false;
} else {
viewModel.isFieldsSynced = true;
b.setText("A changed");
}
}
});
viewModel.bEditData.observe(this, new Observer<String>() {
@Override
public void onChanged(String s) {
if (!b.getText().toString().equals(s)) {
b.setText(s);
}
if (viewModel.isFieldsSynced) {
viewModel.isFieldsSynced = false;
} else {
viewModel.isFieldsSynced = true;
a.setText("B changed");
}
}
});
}
class AListener implements TextWatcher {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
}
@Override
public void afterTextChanged(Editable s) {
System.out.println("A text Changed");
viewModel.aEditData.setValue(s.toString());
}
}
class BListener implements TextWatcher {
@Override
public void beforeTextChanged(CharSequence s, int start, int count, int after) {
}
@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
}
@Override
public void afterTextChanged(Editable s) {
System.out.println("B text changed");
viewModel.bEditData.setValue(s.toString());
}
}
}
package marabillas.loremar.edittextmvvm;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;
public class AViewModel extends ViewModel {
public boolean isFieldsSynced = false;
public MutableLiveData<String> aEditData = new MutableLiveData<>();
public MutableLiveData<String> bEditData = new MutableLiveData<>();
}
第一个if
逻辑是确定A是否要更新。第二个if
逻辑用于确定是否要更新B。这里的A是EditText,其文本由用户输入更改。 B是需要与A同步的文本的EditText。这对逻辑确保EditText和LiveData仅更新一次。