如何让返回键具有删除编辑内容功能

[DESCRIPTION]

在编辑界面，如果正在编辑，就删除编辑的内容。如果编辑的内容为空，按下返回键就返回上一界面
请问该如何实现?

[SOLUTION]

修改Activity.java中onKeyUp 为如下：
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (getApplicationInfo().targetSDKVersion
>= Build.VERSION_CODES.ECLAIR) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.isTracking()
&& ！event.isCanceled()) {
/// M: Fix ALPS00247686, ALPS00253881 Free test JE issue @{
if (isResumed()) {
View decorView = this.getWindow().getDecorView();//mtk modifyBegin
if(decorView！=null){
View focus = decorView.findFocus();
if(focus！=null&&focus instanceof EditText){
(EditText) editText = (EditText)focus;
CharSequence text = editText.getText();
if(text！=null && text.length()>0){
editText.clear();
return true;
}
}
}
onBackPressed();//MTKmodify END
return true;
} else {
Log.v(TAG, "Tracking Key Up, activity is resumed: " + isResumed());
// Fix sub activity of tab activity which isn't in resumed state
// Return false means didn't handle this key event
return false;
}
/// @}
}
}
return false;
}