Question

当我在edittext中输入数字时，app force会关闭。我希望应用程序在输入值时自动计算BMI，而无需按下按钮。

我对TextWatcher一无所知，但我研究过并提出了这段代码。虽然不行。这有什么不对吗？

public class BodyMassIndex extends Activity implements View.OnClickListener,
    TextWatcher {

double result;
EditText age, height, weight;
ToggleButton sex, cmin, kglb;
TextView tvResult;
double heightInt = 1;
double weightInt = 0;
int ageInt;

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.bmi);
    initialize();

    sex.setOnClickListener(this);
    cmin.setOnClickListener(this);
    kglb.setOnClickListener(this);


}

private void initialize() {
    // TODO Auto-generated method stub

    age = (EditText) findViewById(R.id.etAge);
    height = (EditText) findViewById(R.id.etHeight);
    weight = (EditText) findViewById(R.id.etWeight);
    sex = (ToggleButton) findViewById(R.id.tbSex);
    cmin = (ToggleButton) findViewById(R.id.tbCMIN);
    kglb = (ToggleButton) findViewById(R.id.tbKGLB);
    tvResult = (TextView) findViewById(R.id.tvResult);
    age.addTextChangedListener(this);
    height.addTextChangedListener(this);
    weight.addTextChangedListener(this);
}

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

    switch (v.getId()) {
    case R.id.tbCMIN:
        heightInt = heightInt * 0.0254;
        break;
    case R.id.tbKGLB:
        weightInt = weightInt * 0.45359237;
        break;
    }

}

@Override
public void afterTextChanged(Editable s) {
    // TODO Auto-generated method stub
    calculate();
}

private void calculate() {
    // TODO Auto-generated method stub
     Editable H = height.getText(), W = weight.getText();

    if(H != null)
        heightInt = Double.parseDouble(H.toString());
    if (W != null)
        weightInt = Double.parseDouble(W.toString());

    result = weightInt / (heightInt * heightInt);
    String textResult = "Your BMI is " + result;
    tvResult.setText(textResult);
}

@Override
public void beforeTextChanged(CharSequence s, int start, int count,
        int after) {
    // TODO Auto-generated method stub


}

@Override
public void onTextChanged(CharSequence s, int start, int before, int count) {
    // TODO Auto-generated method stub

    }
}

Answer 1

从http://developer.android.com/reference/android/text/TextWatcher.html关于afterTextChanged方法："but be careful not to get yourself into an infinite loop, because any changes you make will cause this method to be called again recursively....you can use setSpan(Object, int, int, int) in onTextChanged（CharSequence，int，int，int）“

Answer 2

你已经拥有：

 height = (EditText) findViewById(R.id.etHeight);
    weight = (EditText) findViewById(R.id.etWeight);

只改变calculate（）方法：

private void calculate()
{
//remove the Editable thing declaration...
heightInt = Double.parseDouble(height.getText().toString());
wightInt = Double.parseDouble(weight.getText().toString());
result = weightInt / (heightInt * heightInt);
String textResult = "Your BMI is " + result;
tvResult.setText(textResult);

}

P.S：我们假设EditText只包含一个数字而不包含字母。信件将强制关闭应用程序。所以你必须检查一下。

如何使用TextWatcher从edittext自动获取值并将它们相乘？

2 个答案: