Question

我正在制作一个使用TextWatcher的长度转换器。缩短的代码是

 v1.addTextChangedListener(new 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) {
                val1=Double.parseDouble(v1.getText().toString()); 
                val2=InchToCm(val1); 
                val3=InchToMl(val1);
                val4=InchToKm(val1);
                val5=InchToM(val1);
                val6=InchToY(val1);
                val7=InchToFt(val1);
                val8=InchToLg(val1);
                val9=InchToLgn(val1);
                val11=InchTomm(val1);
                val12=InchToNm(val1);


                v2. setText(Double.toString(val2)); 
                v3. setText(Double.toString(val3)); 
                v4. setText(Double.toString(val4)); 
                v5. setText(Double.toString(val5)); 
                v6. setText(Double.toString(val6)); 
                v7. setText(Double.toString(val7)); 
                v8. setText(Double.toString(val8));
                v9. setText(Double.toString(val9)); 
                v11. setText(Double.toString(val11)); 
                v12. setText(Double.toString(val12));

            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });
     v2.addTextChangedListener(new 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) {
                val2=Double.parseDouble(v2.getText().toString()); 
                val1=CmToInch(val2);
                val3=CmToMl(val2);
                val4=CmToKm(val2);
                val5=CmToM(val2);
                val6=CmToY(val2);
                val7=CmToFt(val2);
                val8=CmToLg(val2);
                val9=CmToLgn(val2);
                val11=CmTomm(val2);
                val12=CmToNm(val2);

                v1. setText(Double.toString(val1)); 
                v3. setText(Double.toString(val3)); 
                v4. setText(Double.toString(val4)); 
                v5. setText(Double.toString(val5)); 
                v6. setText(Double.toString(val6)); 
                v7. setText(Double.toString(val7)); 
                v8. setText(Double.toString(val8));
                v9. setText(Double.toString(val9)); 
                v11. setText(Double.toString(val11)); 
                v12. setText(Double.toString(val12));

            }

            @Override
            public void afterTextChanged(Editable s) {

            }
        });

我得到一个stackoverflow错误。如果我完全删除了v2的textwatcher代码.v1的文本观察器工作得很好.. 我只是希望我的所有edittext都能与textwatcher一起使用。我错过了什么？我应该改变什么？

继承logcat

08-20 20:31:28.122: E/AndroidRuntime(30377): FATAL EXCEPTION: main
08-20 20:31:28.122: E/AndroidRuntime(30377): java.lang.StackOverflowError
08-20 20:31:28.122: E/AndroidRuntime(30377):    at           android.text.TextUtils.getChars(TextUtils.java:77)
08-20 20:31:28.122: E/AndroidRuntime(30377): android.text.TextUtils.indexOf(TextUtils.java:110)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at     android.text.StaticLayout.generate(StaticLayout.java:182)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.text.DynamicLayout.reflow(DynamicLayout.java:284)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.text.DynamicLayout.<init>(DynamicLayout.java:170)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.makeSingleLayout(TextView.java:6078)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.makeNewLayout(TextView.java:5976)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.checkForRelayout(TextView.java:6515)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.setText(TextView.java:3787)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.setText(TextView.java:3645)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.EditText.setText(EditText.java:80)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.setText(TextView.java:3620)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at com.tdx.simplelegthconverter.MainActivity$1.onTextChanged(MainActivity.java:55)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.sendOnTextChanged(TextView.java:7338)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.setText(TextView.java:3790)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.setText(TextView.java:3645)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.EditText.setText(EditText.java:80)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at android.widget.TextView.setText(TextView.java:3620)
08-20 20:31:28.122: E/AndroidRuntime(30377):    at   com.tdx.simplelegthconverter.MainActivity$2.onTextChanged(MainActivity.java:95)

Answer 1

您正在v1和v2之间创建无限循环的文本更改。

每当您在v1中编辑某些内容时，它TextWatcher会设置v2的文本，而后者会触发v2＆＃39; onTextChanged()的{{1}}。现在，v2＆＃39; TextWatcher设置v1的文本（再次触发v1的TextWatcher）。这将创建一个永无止境的循环，您将获得StackOverflow异常。

您必须更改代码流。

编辑：我正在展示一个例子，如何摆脱两个EditText字段的StackOverflow错误。您可以根据需要对尽可能多的EditTexts进行类似的编码。

首先，您可以像这样扩展TextWatcher（这将帮助您保持代码的组织。并且，您可以对所有EditTexts使用相同的TextWatcher）：

onTextChanged()

诀窍是在调用class MyInputWatcher implements TextWatcher { private EditText et; private MyInputWatcher(EditText editText) { et = editText; } @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) { } @Override public void onTextChanged(CharSequence s, int start, int before, int count) { switch (et.getId()) { case R.id.editText1: { v2.removeTextChangedListener(watcher2); v2.setText(s);// set whatever text you want to set in editText2 v2.addTextChangedListener(watcher2); //add the above 3 lines of code for other EditTexts, too (if any) break; } case R.id.editText2: { v1.removeTextChangedListener(watcher1); v1.setText(s); // set whatever text you want to set in editText1 v1.addTextChangedListener(watcher1); break; } } } @Override public void afterTextChanged(Editable s) { } }之前删除onTextChangeListeners。然后，在完成设置文本后再将它们添加回来。

声明这些成员变量：

setText()

现在，在onCreate（）方法中，实现：

private EditText v1, v2;
private MyInputWatcher watcher1, watcher2;

为方便起见，整个Activity类如下所示：

v1 = (EditText)findViewById(R.id.editText1);
v2 = (EditText)findViewById(R.id.editText2);

watcher1 = new MyInputWatcher(v1);
watcher2 = new MyInputWatcher(v2);

v1.addTextChangedListener(watcher1);
v2.addTextChangedListener(watcher2);

Answer 2

不要在onTextChanged（）中执行setText，它会导致递归。

您可以尝试以下方法：从onTextChange（）内部执行setText时设置一个布尔变量。这个布尔变量将有助于识别onTextChange被调用，因为文本是以编程方式而不是用户更改的，因此避免了递归

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
                      if(isTextChangedByUser){
                          //calculate and set different values only when user has changed       values
                           editext.setText("programmatically setting the text,change the flag")
                           isTextChangedByUser=false;
                       }else{
                           //to avoid recursion
                            return;
                       }
        }

第二次调用onTextChanged时，它只会返回，因为isTextChangeByUser标志为false。这样我们就会避免递归。

或者，为了使实现更简单，您可以在每个editext旁边放置一个“计算”按钮。您只能在用户按下此按钮时开始计算，而不是在文本更改时开始计算。

Textwatcher给出Stackoverflow错误

2 个答案: