android 之EditText輸入檢測，androidedittext

android 之EditText輸入檢測，androidedittext

最近開發一個功能的時候發生一個故事,其情節如下:

功能其實不複雜,其中需要一個EditText來擷取使用者輸入的資訊.於是,我做了一個Dialog來顯示我的輸入介面(代碼如下):

mAlertDialog = new AlertDialog.Builder(this)//, android.R.style.Theme_Holo_Light                .setIcon(R.drawable.ic_dialog_info_light)                .setTitle(R.string.model_rename_device)                .setView(createDialogView(deviceName))                .setPositiveButton(android.R.string.ok,                        new DialogInterface.OnClickListener() {                            public void onClick(DialogInterface dialog, int which) {                                //String deviceName = mDeviceNameView.getText().toString();                                reset_success=false;                                reset_model_name(mDeviceNameView.getText().toString());//finish();                            }                        })                .setNegativeButton(android.R.string.cancel,                new DialogInterface.OnClickListener() {                            public void onClick(DialogInterface dialog, int which) {//finish();                            }                        }).setOnDismissListener(new DialogInterface.OnDismissListener() {@Overridepublic void onDismiss(DialogInterface arg0) {if(reset_success){start_confir_ResetPhone();}else{finish();}}})                .create();mAlertDialog.getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_VISIBLE);        mAlertDialog.show();

    private View createDialogView(String deviceName) {        final LayoutInflater layoutInflater = (LayoutInflater)this            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);        View view = layoutInflater.inflate(R.layout.dialog_edittext, null);        mDeviceNameView = (EditText) view.findViewById(R.id.edittext);        mDeviceNameView.setFilters(new InputFilter[] {                new Utf8ByteLengthFilter(MODEL_NAME_MAX_LENGTH_BYTES)        });        mDeviceNameView.setText(deviceName);    // set initial value before adding listener        mDeviceNameView.addTextChangedListener(this);        mDeviceNameView.setOnEditorActionListener(new TextView.OnEditorActionListener() {            @Override            public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {                if (actionId == EditorInfo.IME_ACTION_DONE) {                    reset_model_name(v.getText().toString());                    mAlertDialog.dismiss();//finish();                    return true;    // action handled                } else {                //finish();                    return false;   // not handled                }            }        });mDeviceNameView.setSelection(mDeviceNameView.length());        return view;    }

實現起來很簡單!不過當我把使用者輸入的字串儲存起來時候,問題就來了!

原來這個使用者輸入的字串需要儲存在一段我們自己配置的nv裡面,重要的是,分給我儲存的字串的空間只有20個byte,沒有錯就是byte. 所以很簡單,輸入的字元最多不能超過20個字元,由於是byte類型,所以對於輸入的字元必須做檢測,其字元必須在一個byte取值空間(0-127)裡面.實際上就是asic碼.

所以需要對輸入的字元檢測.

為了能夠即時檢測EditText輸入的字元你需要EditText.addTextChangedListener()來添加一個TextWatcher的檢測器,並且實現其中的方法:

public void afterTextChanged(Editable s)

public void beforeTextChanged(CharSequence s, int start, int count, int after)

public void onTextChanged(CharSequence s, int start, int before, int count)

首當其衝想到的辦法是在afterTextChanged方法裡面判斷當前輸入的字元是否時正確的字元,如果不是就通過Editable s來更改:s.delete()來刪除.或者直接使用這個EditText的去從新設定輸入的字元:setText();

其實,這兩個辦法都不行,當快速輸入不對的字元時候就會出現異常,很顯然時同步的問題.

很快我給出來另個解決方案:在onTextChanged()裡面檢測是否有異常的字元,如果有則通過Handler發送訊息的形式來處理.

public void onTextChanged(CharSequence s, int start, int before, int count) {for(int i=0; i < count; i++){if(s.charAt(i+start) > 127 || s.charAt(i+start) < 0){Message msg = mHandler.obtainMessage(handleMessage_detection_MG);msg.obj = s;mHandler.sendMessage(msg);break;}}//Log.d(DEBUG_STR,"onTextChanged str="+s.toString()+"start="+start+"; before="+before+"; count="+count);}

    Handler mHandler = new Handler() {        public void handleMessage(Message msg) {switch (msg.what) {case handleMessage_detection_MG: InptText_Error_correction((CharSequence) msg.obj);break;case handleMessage_blue_name_MG: InptText_rename_blue((String) msg.obj);break;default:break;}}    };

private void InptText_Error_correction(CharSequence chars){if(chars != null){StringBuilder str_b = new StringBuilder(chars);char temp;int start_indx = -1;for(int i = 0; i < str_b.length(); i++){temp = str_b.charAt(i);if(temp > 127 || temp < 0){if(start_indx < 0){start_indx = i;}str_b.deleteCharAt(i);}}mDeviceNameView.setText(str_b.toString());if(start_indx < 0){start_indx = mDeviceNameView.length();}mDeviceNameView.setSelection(start_indx);Toast.makeText(Rename_model_activity.this, getString(R.string.set_name_Error_Character_notice),Toast.LENGTH_SHORT).show();}}

最後要說的是:對於輸入字元的限制可以通過EditText.setFilters()來配置:

        mDeviceNameView.setFilters(new InputFilter[] {                new Utf8ByteLengthFilter(MODEL_NAME_MAX_LENGTH_BYTES)        });

MODEL_NAME_MAX_LENGTH_BYTES時輸入字元的最大長度,Utf8ByteLengthFilter是InputFilter的子類.這裡就是對輸入長度的適配.其實你會很快發現!InputFilter就是一個對輸入字元的檢測器.所以對於輸入字元錯誤偵測其實不用那麼麻煩,其實InputFilter完全可以解決.實現他的方法:    public CharSequence filter(CharSequence source, int start, int end,                               Spanned dest, int dstart, int dend) 

對於輸入的錯誤字元,位元組返回""就可以:

        for (int i = start; i < end; i++) {
            char c = source.charAt(i);

            if(c > 127 || c < 0){
                return "";
            }

        }