android 状态机的作用,Android 状态机、状态模式 基础框架实现
一、StateMachine 要解決的問題
從設(shè)計模式的角度來講，狀態(tài)模式和策略模式類圖是一樣的，所以工作原理也類似。但相比較于策略模式，狀態(tài)模式需要管理好狀態(tài)樹，以及維護狀態(tài)對象的生命周期。
所以，將 Android 源代碼中 WifiStateMachine 所依賴使用的狀態(tài)機框架拿過來，用來生成狀態(tài)樹以及管理狀態(tài)生命周期。
二、使用方式
dependencies {
implementation fileTree(dir: 'libs', include: ['*.jar'])
...
implementation 'com.github.hailouwang:statemachine:1.0.0'
}
三、Demo 案例
1、單狀態(tài) 案例
public static void main(String args[]){
testHelloWorld();
}
static class HelloWorld extends StateMachine {
HelloWorld(String name) {
super(name);
addState(mState1);
setInitialState(mState1);
}
public static HelloWorld makeHelloWorld() {
HelloWorld hw = new HelloWorld("hlwang");
hw.start();
return hw;
}
class State1 extends State {
@Override
public boolean processMessage(Message msg) {
log("Hello World");
return HANDLED;
}
}
State1 mState1 = new State1();
}
void testHelloWorld() {
HelloWorld hw = HelloWorld.makeHelloWorld();
hw.sendMessage(hw.obtainMessage());
}
2、多狀態(tài)協(xié)同 案例
構(gòu)建如下狀態(tài)樹：
mP1 mP2
/
mS2 mS1
public static void main(String args[]){
testMoreStateTransaction();
}
static class Hsm1 extends StateMachine {
public static final int CMD_1 = 1;
public static final int CMD_2 = 2;
public static final int CMD_3 = 3;
public static final int CMD_4 = 4;
public static final int CMD_5 = 5;
public static Hsm1 makeHsm1() {
Log.d("hlwang", "makeHsm1 E");
Hsm1 sm = new Hsm1("hlwang");
sm.start();
Log.d("hlwang", "makeHsm1 X");
return sm;
}
Hsm1(String name) {
super(name);
log("ctor E");
// Add states, use indentation to show hierarchy
addState(mP1);
addState(mS1, mP1);
addState(mS2, mP1);
addState(mP2);
// Set the initial state
setInitialState(mS1);
log("ctor X");
}
class P1 extends State {
@Override
public void enter() {
log("mP1.enter");
}
@Override
public boolean processMessage(Message message) {
boolean retVal;
log("mP1.processMessage what=" + message.what);
switch (message.what) {
case CMD_2:
// CMD_2 will arrive in mS2 before CMD_3
sendMessage(obtainMessage(CMD_3));
deferMessage(message);
transitionTo(mS2);
retVal = HANDLED;
break;
default:
// Any message we don't understand in this state invokes unhandledMessage
retVal = NOT_HANDLED;
break;
}
return retVal;
}
@Override
public void exit() {
log("mP1.exit");
}
}
class S1 extends State {
@Override
public void enter() {
log("mS1.enter");
}
@Override
public boolean processMessage(Message message) {
log("S1.processMessage what=" + message.what);
if (message.what == CMD_1) {
// Transition to ourself to show that enter/exit is called
transitionTo(mS1);
return HANDLED;
} else {
// Let parent process all other messages
return NOT_HANDLED;
}
}
@Override
public void exit() {
log("mS1.exit");
}
}
class S2 extends State {
@Override
public void enter() {
log("mS2.enter");
}
@Override
public boolean processMessage(Message message) {
boolean retVal;
log("mS2.processMessage what=" + message.what);
switch (message.what) {
case (CMD_2):
sendMessage(obtainMessage(CMD_4));
retVal = HANDLED;
break;
case (CMD_3):
deferMessage(message);
transitionTo(mP2);
retVal = HANDLED;
break;
default:
retVal = NOT_HANDLED;
break;
}
return retVal;
}
@Override
public void exit() {
log("mS2.exit");
}
}
class P2 extends State {
@Override
public void enter() {
log("mP2.enter");
sendMessage(obtainMessage(CMD_5));
}
@Override
public boolean processMessage(Message message) {
log("P2.processMessage what=" + message.what);
switch (message.what) {
case (CMD_3):
break;
case (CMD_4):
break;
case (CMD_5):
transitionToHaltingState();
break;
}
return HANDLED;
}
@Override
public void exit() {
log("mP2.exit");
}
}
@Override
public void onHalting() {
log("halting");
synchronized (this) {
this.notifyAll();
}
}
P1 mP1 = new P1();
S1 mS1 = new S1();
S2 mS2 = new S2();
P2 mP2 = new P2();
}
四、備注
1、處于狀態(tài)子樹的狀態(tài)，如果未處理請求，會將請求交給父狀態(tài)繼續(xù)處理。如上案例所示，S1 未處理的請求，P1 會接手處理。
總結(jié)
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