对于Android用户而言，一般都会使用第三方的输入法。可是，在输入密码时（尤其是支付相关的密码），使用第三方输入法有极大的安全隐患。目前很多网银类的APP和支付宝等软件在用户输入密码时，都会弹出自定义的输入法而不是直接使用系统输入法。
本文介绍的就是如何实现一个简单的自定义输入法。当然，也可以自己写一个Dialog加上几十个按钮让用户输入，只不过这样显得不够专业。
（一）首先上效果图：
1.前面两个输入框使用了自定义的输入法：
2.第三个输入框没有进行任何设置，因此将使用默认的输入法：
（二）代码简介：
1.主页面布局，由3个输入框加上一个android.inputmethodservice.KeyboardView组成。android.inputmethodservice.KeyboardView是一个系统自带的继承自View的组件，但是它不在android.view这个包下面，，因此这里需要写上完整的包名。
<RelativeLayout xmlns:android=""android:layout_width="match_parent"android:layout_height="match_parent"><!–前两个EditText均使用自定义的输入法–><EditTextandroid:id="@+id/input_password"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_margin="8dp"android:hint="one password"android:layout_alignParentTop="true"android:inputType="textPassword" /><EditTextandroid:id="@+id/input_password2"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@+id/input_password"android:layout_margin="8dp"android:hint="another password"android:inputType="textPassword" /><!–这个EditText使用默认的输入法–><EditTextandroid:id="@+id/input_normal_text"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_below="@+id/input_password2"android:layout_margin="8dp"android:hint="normal text" /><android.inputmethodservice.KeyboardViewandroid:id="@+id/keyboardview"android:layout_width="match_parent"android:layout_height="wrap_content"android:layout_alignParentBottom="true"android:layout_centerHorizontal="true"android:focusable="true"android:focusableInTouchMode="true"android:visibility="gone" /></RelativeLayout>2.KeyboardView是一个显示输入法的容器控件，使用时需要设置具体的输入法面板内容。
（1）首先在res下新建xml目录，然后创建文件keys_layout.xml，即输入法面板的内容。每个row表示一行，Keyboad的属性keyWidth和keyHeight表示每个按键的大小，25%p表示占父组件的25%. Key的属性codes表示该按键的编号（点击时系统回调方法中会返回这个值，用以区分不同的按键），keyLabel表示按键上面显示的文字。还有很多其它的属性，不再陈述。
<?xml version="1.0" encoding="utf-8"?><Keyboard xmlns:android=""android:keyWidth="25%p"android:keyHeight="10%p"><Row><Keyandroid:codes="55"android:keyLabel="7"android:keyEdgeFlags="left" /><Keyandroid:codes="56"android:keyLabel="8" /><Keyandroid:codes="57"android:keyLabel="9" /><!–删除按键长按时连续响应–> <Key android:codes="60001" android:keyLabel="DEL" android:isRepeatable="true" /></Row><Row><Keyandroid:codes="52"android:keyLabel="4"android:keyEdgeFlags="left" /><Keyandroid:codes="53"android:keyLabel="5" /><Keyandroid:codes="54"android:keyLabel="6" /><Keyandroid:codes="48"android:keyLabel="0" /></Row><Row><Keyandroid:codes="49"android:keyLabel="1"android:keyEdgeFlags="left" /><Keyandroid:codes="50"android:keyLabel="2" /><Keyandroid:codes="51"android:keyLabel="3" /><Keyandroid:codes="60002"android:keyLabel="Cancel" /></Row></Keyboard>（2）为了使用方便，新建一个类：KeyboardBuilder.java，用于初始化自定义输入法和绑定EditText，代码如下：public class KeyboardBuilder {private static final String TAG = "KeyboardBuilder";private Activity mActivity;private KeyboardView mKeyboardView;public KeyboardBuilder(Activity ac, KeyboardView keyboardView, int keyBoardXmlResId) {mActivity = ac;mKeyboardView = keyboardView;Keyboard mKeyboard = new Keyboard(mActivity, keyBoardXmlResId);// Attach the keyboard to the viewmKeyboardView.setKeyboard(mKeyboard);// Do not show the preview balloonsmKeyboardView.setPreviewEnabled(false);KeyboardView.OnKeyboardActionListener keyboardListener = new KeyboardView.OnKeyboardActionListener() {@Overridepublic void onKey(int primaryCode, int[] keyCodes) {// Get the EditText and its EditableView focusCurrent = mActivity.getWindow().getCurrentFocus();if (focusCurrent == null || !(focusCurrent instanceof EditText)) {return;}EditText edittext = (EditText) focusCurrent;Editable editable = edittext.getText();int start = edittext.getSelectionStart();// Handle keyif (primaryCode == Constant.CodeCancel) {hideCustomKeyboard();} else if (primaryCode == Constant.CodeDelete) {if (editable != null && start > 0) {editable.delete(start – 1, start);}} else {// Insert charactereditable.insert(start, Character.toString((char) primaryCode));}}@Overridepublic void onPress(int arg0) {}@Overridepublic void onRelease(int primaryCode) {}@Overridepublic void onText(CharSequence text) {}@Overridepublic void swipeDown() {}@Overridepublic void swipeLeft() {}@Overridepublic void swipeRight() {}@Overridepublic void swipeUp() {}};mKeyboardView.setOnKeyboardActionListener(keyboardListener);}//绑定一个EditTextpublic void registerEditText(EditText editText) {// Make the custom keyboard appeareditText.setOnFocusChangeListener(new View.OnFocusChangeListener() {@Overridepublic void onFocusChange(View v, boolean hasFocus) {if (hasFocus) {showCustomKeyboard(v);} else {hideCustomKeyboard();}}});editText.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {Log.d(TAG, "onClick");showCustomKeyboard(v);}});editText.setOnTouchListener(new View.OnTouchListener() {@Overridepublic boolean onTouch(View v, MotionEvent event) {Log.d(TAG, "onTouch");EditText edittext = (EditText) v;int inType = edittext.getInputType();// Backup the input typeedittext.setInputType(InputType.TYPE_NULL); // Disable standard keyboardedittext.onTouchEvent(event);// Call native handleredittext.setInputType(inType);// Restore input typeedittext.setSelection(edittext.getText().length());return true;}});}public void hideCustomKeyboard() {mKeyboardView.setVisibility(View.GONE);mKeyboardView.setEnabled(false);}public void showCustomKeyboard(View v) {mKeyboardView.setVisibility(View.VISIBLE);mKeyboardView.setEnabled(true);if (v != null) {((InputMethodManager) mActivity.getSystemService(Activity.INPUT_METHOD_SERVICE)).hideSoftInputFromWindow(v.getWindowToken(), 0);}}public boolean isCustomKeyboardVisible() {return mKeyboardView.getVisibility() == View.VISIBLE;}3.最后是主Activity的代码，这里就很简单了。/** * 自定义安全输入法 */public class MainActivity extends ActionBarActivity {private KeyboardBuilder builder;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);getWindow().setSoftInputMode(WindowManager.LayoutParams.SOFT_INPUT_STATE_ALWAYS_HIDDEN);KeyboardView keyboardView = (KeyboardView) findViewById(R.id.keyboardview);builder = new KeyboardBuilder(this, keyboardView, R.xml.keys_layout);EditText editText = (EditText) findViewById(R.id.input_password);builder.registerEditText(editText);EditText editText2 = (EditText) findViewById(R.id.input_password2);builder.registerEditText(editText2);}@Overridepublic void onBackPressed() {if (builder != null && builder.isCustomKeyboardVisible()) {builder.hideCustomKeyboard();} else {this.finish();}}}
参考文档：
一错再错，把握正确的方向，
