场景：android 应用监听输入法按键事件【例如搜索和回车键等】的整个流程分析

android 应用监听输入法按键事件【比如搜索和回车键等】的整个流程分析

继承于InputMethodService类的服务代码如下：

int keyCode = sKey.getKeyCode();

KeyEvent eDown = new KeyEvent(0, 0, KeyEvent.ACTION_DOWN,

keyCode, 0, 0, 0, 0, KeyEvent.FLAG_SOFT_KEYBOARD);

KeyEvent eUp = new KeyEvent(0, 0, KeyEvent.ACTION_UP, keyCode,

0, 0, 0, 0, KeyEvent.FLAG_SOFT_KEYBOARD);

onKeyDown(keyCode, eDown);

onKeyUp(keyCode, eUp);

上面的代码：把有关按键下发给应用，即应用监听输入法按键事件

@Override

public boolean onKeyDown(int keyCode, KeyEvent event) {

if (processKey(event, 0 != event.getRepeatCount())) return true;

return super.onKeyDown(keyCode, event);

}

@Override

public boolean onKeyUp(int keyCode, KeyEvent event) {

if (processKey(event, true)) return true;

return super.onKeyUp(keyCode, event);

}

上面的down和up，我们重点看onKeyUp，跟踪下日志，是下面直接返回true了

if (processKey(event, true)) return true;

进入该方法，在该方法里面有如下代码为其覆盖代码：

if (processFunctionKeys(keyCode, realAction)) {

return true;

}

再进入该方法processFunctionKeys，跟踪其走入了下面代码：

if (keyCode == KeyEvent.KEYCODE_ENTER) {

if (!realAction){

Log.d(TAG,"processFunctionKeys call KEYCODE_ENTER return");

return true;

}

sendKeyChar('\n');

return true;

}

因为上面realAction为传进来的true，所以执行了如下

sendKeyChar('\n');

进入该方法，该方法在InputMethodService中

public void sendKeyChar(char charCode) {

switch (charCode) {

case '\n': // Apps may be listening to an enter key to perform an action

if (!sendDefaultEditorAction(true)) {

sendDownUpKeyEvents(KeyEvent.KEYCODE_ENTER);

}

break;

default:

// Make sure that digits go through any text watcher on the client side.

if (charCode >= '0' && charCode <= '9') {

sendDownUpKeyEvents(charCode - '0' + KeyEvent.KEYCODE_0);

} else {

InputConnection ic = getCurrentInputConnection();

if (ic != null) {

ic.commitText(String.valueOf((char) charCode), 1);

}

}

break;

}

}

因为传进入的是'\n'，所以执行了如下：

case '\n': // Apps may be listening to an enter key to perform an action

if (!sendDefaultEditorAction(true)) {

sendDownUpKeyEvents(KeyEvent.KEYCODE_ENTER);

}

break;

看上面注释：// Apps may be listening to an enter key to perform an action，很清楚吧，呵呵，来看看这个方法吧

public boolean sendDefaultEditorAction(boolean fromEnterKey) {

EditorInfo ei = getCurrentInputEditorInfo();

if (ei != null &&

(!fromEnterKey || (ei.imeOptions &

EditorInfo.IME_FLAG_NO_ENTER_ACTION) == 0) &&

(ei.imeOptions & EditorInfo.IME_MASK_ACTION) !=

EditorInfo.IME_ACTION_NONE) {

// If the enter key was pressed, and the editor has a default

// action associated with pressing enter, then send it that

// explicit action instead of the key event.

InputConnection ic = getCurrentInputConnection();

if (ic != null) {

ic.performEditorAction(ei.imeOptions&EditorInfo.IME_MASK_ACTION);

}

return true;

}

return false;

}

上面这个方法只是通知：让编辑器执行它,表示它可以做一个动作:

/**

* Have the editor perform an action it has said it can do.

*/

public boolean performEditorAction(int editorAction);

/**

* Set of bits in {@link #imeOptions} that provide alternative actions

* associated with the "enter" key. This both helps the IME provide

* better feedback about what the enter key will do, and also allows it

* to provide alternative mechanisms for providing that command.

*/

public static final int IME_MASK_ACTION = 0x000000ff;

我们来看这个方法EditableInputConnection中，有关为什么是EditableInputConnection看我之前的帖子就会明白了

@Override

public boolean performEditorAction(int actionCode) {

if (DEBUG) Log.v(TAG, "performEditorAction " + actionCode);

mTextView.onEditorAction(actionCode);

return true;

}

一般应用程序想要监听回车或搜索按键则，如下写法：

edittext.setOnEditorActionListener(new TextView.OnEditorActionListener() {

@Override

public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {

/*判断是否是“GO”键*/

if(actionId == EditorInfo.IME_ACTION_GO){

edittext.setText("success");

return true;

}

return false;

}

});

上面这个调用的是TextView中的接口

/**

* Interface definition for a callback to be invoked when an action is

* performed on the editor.

*/

public interface OnEditorActionListener {

/**

* Called when an action is being performed.

*

* @param v The view that was clicked.

* @param actionId Identifier of the action. This will be either the

* identifier you supplied, or {@link EditorInfo#IME_NULL

* EditorInfo.IME_NULL} if being called due to the enter key

* being pressed.

* @param event If triggered by an enter key, this is the event;

* otherwise, this is null.

* @return Return true if you have consumed the action, else false.

*/

boolean onEditorAction(TextView v, int actionId, KeyEvent event);

}

上面的又是怎么实现的呢?

/**

* Set a special listener to be called when an action is performed

* on the text view. This will be called when the enter key is pressed,

* or when an action supplied to the IME is selected by the user. Setting

* this means that the normal hard key event will not insert a newline

* into the text view, even if it is multi-line; holding down the ALT

* modifier will, however, allow the user to insert a newline character.

*/

public void setOnEditorActionListener(OnEditorActionListener l) {

if (mInputContentType == null) {

mInputContentType = new InputContentType();

}

mInputContentType.onEditorActionListener = l;

}

我们看到了OnEditorActionListener l赋值给了mInputContentType.onEditorActionListener

那么我们再回到上面EditableInputConnection中的方法：

@Override

public boolean performEditorAction(int actionCode) {

if (DEBUG) Log.v(TAG, "performEditorAction " + actionCode);

mTextView.onEditorAction(actionCode);

return true;

}

进入如下方法：

mTextView.onEditorAction(actionCode);

public void onEditorAction(int actionCode) {

final InputContentType ict = mInputContentType;

if (ict != null) {

if (ict.onEditorActionListener != null) {

if (ict.onEditorActionListener.onEditorAction(this,

actionCode, null)) {

return;

}

}

看到了吧，之前放入mInputContentType的onEditorActionListener现在赋值给了InputContentType ict，然后执行了

ict.onEditorActionListener.onEditorAction(this,

actionCode, null)

现在我们明白了吧，搜索和回车等等按键就是这么实现回调的