android 之EditText输入检测

最近开发一个功能的时候发生一个故事,其情节如下:

功能其实不复杂,其中需要一个EditText来获取用户输入的信息.于是,我做了一个Dialog来显示我的输入界面(代码如下):

		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() {
									@Override
									public 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;
    }

原来这个用户输入的字符串需要存储在一段我们自己配置的nv里面,重要的是,分给我存储的字符串的空间只有20个byte,没有错就是byte. 所以很简单,输入的字符最多不能超过20个字符,由于是byte类型,所以对于输入的字符必须做检测,其字符必须在一个byte取值空间(0-127)里面.实际上就是asic码.

所以需要对输入的字符检测.

为了能够实时检测EditText输入的字符你需要EditText.addTextChangedListener()来添加一个TextWatcher的检测器,并且实现其中的方法:

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)

首当其冲想到的办法是在afterTextChanged方法里面判断当前输入的字符是否时正确的字符,如果不是就通过Editable s来更改:s.delete()来删除.或者直接使用这个EditText的去从新设置输入的字符:setText();

其实,这两个办法都不行,当快速输入不对的字符时候就会出现异常,很显然时同步的问题.

很快我给出来另个解决方法:在onTextChanged()里面检测是否有异常的字符,如果有则通过Handler发送消息的形式来处理.

	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();

		}
	}

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

MODEL_NAME_MAX_LENGTH_BYTES时输入字符的最大长度,Utf8ByteLengthFilter是InputFilter的子类.这里就是对输入长度的适配.
其实你会很快发现!InputFilter就是一个对输入字符的检测器.所以对于输入字符错误检测其实不用那么麻烦,其实InputFilter完全可以解决.实现他的方法:
    public CharSequence filter(CharSequence source, int start, int end,
                               Spanned dest, int dstart, int dend) 

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

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

        }