Input system learning ----- inputfilter

Android There is 2 individual InputFilter, What we usually find is text.InputFilter,

Here we are talking about input dependent view.InputFilter,

Input In the distribution process, it is necessary to determine whether or not InputFilter, If it's set up ,input The process will come to InputFilter in ,

see InputFilter The definition of , I inherited it binder Of stub object , It seems that it can be used as binder The service object transfers data in the process .

 * @hide
 */
public abstract class InputFilter extends IInputFilter.Stub {
  

to glance at IInputFilter The definition of ,

frameworks/base/core/java/android/view/IInputFilter.aidl

package android.view;

import android.view.IInputFilterHost;
import android.view.InputEvent;

/**
 * Interface for implementing an filter which observes and
 * potentially transforms the input event stream in the system.
 *
 * @hide
 */
oneway interface IInputFilter {
    void install(IInputFilterHost host);
    void uninstall();
    void filterInputEvent(in InputEvent event, int policyFlags);
}

It can be seen that ,InputEvent,MotionEvent Objects can be serialized and passed through binder delivery .

InputFilter It defines handler For asynchronous processing , Compile the... Of the receiving system input event , Avoid systematic input The process is blocked , We can also call filterInputEvent Method to actively inject an event ,

    final public void filterInputEvent(InputEvent event, int policyFlags) {
        mH.obtainMessage(MSG_INPUT_EVENT, policyFlags, 0, event).sendToTarget();
    }

handler The definition of

    private final class H extends Handler {
        public H(Looper looper) {
            super(looper);
        }

        @Override
        public void handleMessage(Message msg) {
            switch (msg.what) {
                case MSG_INSTALL:
                    mHost = (IInputFilterHost) msg.obj;
                    if (mInboundInputEventConsistencyVerifier != null) {
                        mInboundInputEventConsistencyVerifier.reset();
                    }
                    if (mOutboundInputEventConsistencyVerifier != null) {
                        mOutboundInputEventConsistencyVerifier.reset();
                    }
                    onInstalled();
                    break;

                case MSG_UNINSTALL:
                    try {
                        onUninstalled();
                    } finally {
                        mHost = null;
                    }
                    break;

                case MSG_INPUT_EVENT: {
                    final InputEvent event = (InputEvent)msg.obj;
                    try {
                        if (mInboundInputEventConsistencyVerifier != null) {
                            mInboundInputEventConsistencyVerifier.onInputEvent(event, 0);
                        }
                        onInputEvent(event, msg.arg1);
                    } finally {
                        event.recycle();
                    }
                    break;
                }
            }
        }
    }
}

Reference material

Android Auxiliary function --- Global gesture zoom - You know