android MVP模式思考
在软件开发设计中，有多种软件设计模式，如web开发中经典的MVC, 将后台分为三层：Model层，View层和Controller层，其中，Model主要是数据处理，如数据库，文件，或网络数据等；View层是视图层，主要是指前端或后端用于直接展现给用户的页面，Controller层则是负责业务逻辑处理，即将Model中读取的数据显示到View层，同时又将View层触发的操作事件经过业务处理后将数据保存到Model层中。
在android中，可能很多开发者使用的还是mvc模式，比如，在代码中可以发现大量的IxxEntity,IxxDao,IxxDaoImpl,IxxController,IxxControllerImpldengdeng。但是，Android开发中，还有一种不错的开发设计，那就是MVP模式。在Android4.4源码中的InCallUI中，我们会发现就应用了这种模式。
首先，先解释下，什么是MVP，MVP模式其实跟MVC模式的意图是一样的，都是为了将视图，数据和业务层分离开了，从而更好的应用于后续的开发，升级以及维护。其中MVP中的P，代表Presenter，即主持的意思，主要负责业务逻辑处理，跟MVC模式不同的是，在MVP中View层是不允许跟Model层直接交互的。MVP模式的理想场景就是可以只修改View层的界面代码，但是Presenter层和model层不需要修改任何代码，这是因为在android中，开发者面对最多的需求就是界面，变化最多的也是界面，所以mvp模式对android开发来说是一个非常不错的选择，当然，弊端就是，额外增加的代码量也有点多。。。
具体调用逻辑，借用下面网上一张图：
接着，我们来看看android4.4中InCallUI源码中MVP代码的应用。
InCallUI源码路径是在/packages/apps/InCallUI，我们直接看/src/com/android/incallui目录，会发现该目录下有一大堆xxxPresenter的类。其中，AnswerPresenter是处理接听电话的Presenter，CallButtonPresenter是处理拨号盘的Presenter，CallCardPresenter是通话界面的Presenter。在InCallUI中，从所有的界面中抽象出一个接口：Ui，它是一个空接口，它的子类分别对应不同的Ui，因为对应MVP每一个V，它的界面都是不同的，所以需要抽象出一个接口，并且让这个接口继承Ui，具体代码如下：
/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License */ package com.android.incallui; /** * Base class for all presenter ui. */ public interface Ui { }
如前面所说，CallButtonXX是负责拨号盘，对于拨号盘的界面显示，InCallUI抽象了一个继承Ui的接口CallButtonUi（定义在CallButtonPresenter类中），相关代码如下：
public interface CallButtonUi extends Ui { void setEnabled(boolean on); void setMute(boolean on); void enableMute(boolean enabled); void setHold(boolean on); void showHold(boolean show); void enableHold(boolean enabled); void showMerge(boolean show); void showSwap(boolean show); void showAddCall(boolean show); void enableAddCall(boolean enabled); void displayDialpad(boolean on); boolean isDialpadVisible(); void setAudio(int mode); void setSupportedAudio(int mask); void showManageConferenceCallButton(); void showGenericMergeButton(); void hideExtraRow(); void displayManageConferencePanel(boolean on); }
在InCallUI中，抽象类Presenter是所有XXPresenter的父类，他主要实现了跟View交互时所有Presenter都所需的onUiReady和onUiUnready两个方法。具体代码如下：
/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License */ package com.android.incallui; /** * Base class for Presenters. */ public abstract class Presenter<U extends Ui> { private U mUi; /** * Called after the UI view has been created. That is when fragment.onViewCreated() is called. * * @param ui The Ui implementation that is now ready to be used. */ public void onUiReady(U ui) { mUi = ui; } /** * Called when the UI view is destroyed in Fragment.onDestroyView(). */ public final void onUiDestroy(U ui) { onUiUnready(ui); mUi = null; } /** * To be overriden by Presenter implementations. Called when the fragment is being * destroyed but before ui is set to null. */ public void onUiUnready(U ui) { } public U getUi() { return mUi; } }
其中Presenter中的实现CallButtonPresenter的代码如下：
/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License */ package com.android.incallui; import com.android.incallui.AudioModeProvider.AudioModeListener; import com.android.incallui.InCallPresenter.InCallState; import com.android.incallui.InCallPresenter.InCallStateListener; import com.android.incallui.InCallPresenter.IncomingCallListener; import com.android.services.telephony.common.AudioMode; import com.android.services.telephony.common.Call; import com.android.services.telephony.common.Call.Capabilities; import android.telephony.PhoneNumberUtils; /** * Logic for call buttons. */ public class CallButtonPresenter extends Presenter<CallButtonPresenter.CallButtonUi> implements InCallStateListener, AudioModeListener, IncomingCallListener { //省略若干行代码 public CallButtonPresenter() { } @Override public void onUiReady(CallButtonUi ui) { super.onUiReady(ui); AudioModeProvider.getInstance().addListener(this); // register for call state changes last InCallPresenter.getInstance().addListener(this); InCallPresenter.getInstance().addIncomingCallListener(this); } @Override public void onUiUnready(CallButtonUi ui) { super.onUiUnready(ui); InCallPresenter.getInstance().removeListener(this); AudioModeProvider.getInstance().removeListener(this); InCallPresenter.getInstance().removeIncomingCallListener(this); } @Override public void onStateChange(InCallState state, CallList callList) { //省略若干行代码 } @Override public void onIncomingCall(InCallState state, Call call) { onStateChange(state, CallList.getInstance()); } @Override public void onAudioMode(int mode) { if (getUi() != null) { getUi().setAudio(mode); } } @Override public void onSupportedAudioMode(int mask) { if (getUi() != null) { getUi().setSupportedAudio(mask); } } @Override public void onMute(boolean muted) { if (getUi() != null) { getUi().setMute(muted); } } public int getAudioMode() { return AudioModeProvider.getInstance().getAudioMode(); } public int getSupportedAudio() { return AudioModeProvider.getInstance().getSupportedModes(); } public void setAudioMode(int mode) { //省略若干行代码 } /** * Function assumes that bluetooth is not supported. */ public void toggleSpeakerphone() { //省略若干行代码 } public void endCallClicked() { if (mCall == null) { return; } CallCommandClient.getInstance().disconnectCall(mCall.getCallId()); } public void manageConferenceButtonClicked() { getUi().displayManageConferencePanel(true); } public void muteClicked(boolean checked) { Log.d(this, "turning on mute: " + checked); CallCommandClient.getInstance().mute(checked); } public void holdClicked(boolean checked) { if (mCall == null) { return; } Log.d(this, "holding: " + mCall.getCallId()); CallCommandClient.getInstance().hold(mCall.getCallId(), checked); } public void mergeClicked() { CallCommandClient.getInstance().merge(); } public void addCallClicked() { //省略若干行代码 } public void swapClicked() { //省略若干行代码 } public void showDialpadClicked(boolean checked) { //省略若干行代码 } private void updateUi(InCallState state, Call call) { //省略若干行代码 } private void updateExtraButtonRow() { //省略若干行代码 } public void refreshMuteState() { //省略若干行代码 } public interface CallButtonUi extends Ui { void setEnabled(boolean on); void setMute(boolean on); void enableMute(boolean enabled); void setHold(boolean on); void showHold(boolean show); void enableHold(boolean enabled); void showMerge(boolean show); void showSwap(boolean show); void showAddCall(boolean show); void enableAddCall(boolean enabled); void displayDialpad(boolean on); boolean isDialpadVisible(); void setAudio(int mode); void setSupportedAudio(int mask); void showManageConferenceCallButton(); void showGenericMergeButton(); void hideExtraRow(); void displayManageConferencePanel(boolean on); } }
在InCallUI中，除了InCallActivity，其他界面都是由Fragment负责界面，即，每个Fragment都属于MVP中的View，InCallUI中抽象出了一个BaseFragment来作为所有Fragment的父类，BaseFragment代码如下：
/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License */ package com.android.incallui; import android.app.Fragment; import android.os.Bundle; /** * Parent for all fragments that use Presenters and Ui design. */ public abstract class BaseFragment<T extends Presenter<U>, U extends Ui> extends Fragment { private T mPresenter; abstract T createPresenter(); abstract U getUi(); protected BaseFragment() { mPresenter = createPresenter(); } /** * Presenter will be available after onActivityCreated(). * * @return The presenter associated with this fragment. */ public T getPresenter() { return mPresenter; } @Override public void onActivityCreated(Bundle savedInstanceState) { super.onActivityCreated(savedInstanceState); mPresenter.onUiReady(getUi()); } @Override public void onDestroyView() { super.onDestroyView(); mPresenter.onUiDestroy(getUi()); } }
即在BaseFragment或继承自BaseFragment的子Fragment被创建的时候，将V(Fragment)跟P(Presenter)关联，在Fragment被销毁的时候，将V和P解绑。这里我们继续看看CallButtonFragment的代码：
/* * Copyright (C) 2013 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License */ package com.android.incallui; import android.graphics.drawable.LayerDrawable; import android.os.Bundle; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.View.OnClickListener; import android.view.ViewGroup; import android.widget.CompoundButton; import android.widget.ImageButton; import android.widget.PopupMenu; import android.widget.PopupMenu.OnDismissListener; import android.widget.PopupMenu.OnMenuItemClickListener; import android.widget.ToggleButton; import com.android.services.telephony.common.AudioMode; /** * Fragment for call control buttons */ public class CallButtonFragment extends BaseFragment<CallButtonPresenter, CallButtonPresenter.CallButtonUi> implements CallButtonPresenter.CallButtonUi, OnMenuItemClickListener, OnDismissListener, View.OnClickListener, CompoundButton.OnCheckedChangeListener { private ImageButton mMuteButton; private ImageButton mAudioButton; private ImageButton mHoldButton; private ToggleButton mShowDialpadButton; private ImageButton mMergeButton; private ImageButton mAddCallButton; private ImageButton mSwapButton; private PopupMenu mAudioModePopup; private boolean mAudioModePopupVisible; private View mEndCallButton; private View mExtraRowButton; private View mManageConferenceButton; private View mGenericMergeButton; @Override CallButtonPresenter createPresenter() { // TODO: find a cleaner way to include audio mode provider than // having a singleton instance. return new CallButtonPresenter(); } @Override CallButtonPresenter.CallButtonUi getUi() { return this; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { //省略若干行代码 mManageConferenceButton = parent.findViewById(R.id.manageConferenceButton); mManageConferenceButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { getPresenter().manageConferenceButtonClicked(); } }); mGenericMergeButton = parent.findViewById(R.id.cdmaMergeButton); mGenericMergeButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { getPresenter().mergeClicked(); } }); //省略若干行代码 } @Override public void onActivityCreated(Bundle savedInstanceState) { //省略若干行代码 } @Override public void onResume() { if (getPresenter() != null) { getPresenter().refreshMuteState(); } //省略若干行代码 } @Override public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { } @Override public void onClick(View view) { //省略若干行代码 } @Override public void setEnabled(boolean isEnabled) { //省略若干行代码 } @Override public void setMute(boolean value) { mMuteButton.setSelected(value); } @Override public void enableMute(boolean enabled) { mMuteButton.setEnabled(enabled); } @Override public void setHold(boolean value) { mHoldButton.setSelected(value); } @Override public void showHold(boolean show) { mHoldButton.setVisibility(show ? View.VISIBLE : View.GONE); } @Override public void enableHold(boolean enabled) { mHoldButton.setEnabled(enabled); } @Override public void showMerge(boolean show) { mMergeButton.setVisibility(show ? View.VISIBLE : View.GONE); } @Override public void showSwap(boolean show) { mSwapButton.setVisibility(show ? View.VISIBLE : View.GONE); } @Override public void showAddCall(boolean show) { mAddCallButton.setVisibility(show ? View.VISIBLE : View.GONE); } @Override public void enableAddCall(boolean enabled) { mAddCallButton.setEnabled(enabled); } @Override public void setAudio(int mode) { updateAudioButtons(getPresenter().getSupportedAudio()); refreshAudioModePopup(); } @Override public void setSupportedAudio(int modeMask) { updateAudioButtons(modeMask); refreshAudioModePopup(); } @Override public boolean onMenuItemClick(MenuItem item) { //省略若干行代码 } // PopupMenu.OnDismissListener implementation; see showAudioModePopup(). // This gets called when the PopupMenu gets dismissed for *any* reason, like // the user tapping outside its bounds, or pressing Back, or selecting one // of the menu items. @Override public void onDismiss(PopupMenu menu) { Log.d(this, "- onDismiss: " + menu); mAudioModePopupVisible = false; } /** * Checks for supporting modes. If bluetooth is supported, it uses the audio * pop up menu. Otherwise, it toggles the speakerphone. */ private void onAudioButtonClicked() { Log.d(this, "onAudioButtonClicked: " + AudioMode.toString(getPresenter().getSupportedAudio())); if (isSupported(AudioMode.BLUETOOTH)) { showAudioModePopup(); } else { getPresenter().toggleSpeakerphone(); } } /** * Refreshes the "Audio mode" popup if it's visible. This is useful * (for example) when a wired headset is plugged or unplugged, * since we need to switch back and forth between the "earpiece" * and "wired headset" items. * * This is safe to call even if the popup is already dismissed, or even if * you never called showAudioModePopup() in the first place. */ public void refreshAudioModePopup() { if (mAudioModePopup != null && mAudioModePopupVisible) { // Dismiss the previous one mAudioModePopup.dismiss(); // safe even if already dismissed // And bring up a fresh PopupMenu showAudioModePopup(); } } /** * Updates the audio button so that the appriopriate visual layers * are visible based on the supported audio formats. */ private void updateAudioButtons(int supportedModes) { //省略若干行代码 } private boolean isSupported(int mode) { return (mode == (getPresenter().getSupportedAudio() & mode)); } private boolean isAudio(int mode) { return (mode == getPresenter().getAudioMode()); } @Override public void displayDialpad(boolean value) { mShowDialpadButton.setChecked(value); if (getActivity() != null && getActivity() instanceof InCallActivity) { ((InCallActivity) getActivity()).displayDialpad(value); } } @Override public boolean isDialpadVisible() { if (getActivity() != null && getActivity() instanceof InCallActivity) { return ((InCallActivity) getActivity()).isDialpadVisible(); } return false; } @Override public void displayManageConferencePanel(boolean value) { if (getActivity() != null && getActivity() instanceof InCallActivity) { ((InCallActivity) getActivity()).displayManageConferencePanel(value); } } @Override public void showManageConferenceCallButton() { mExtraRowButton.setVisibility(View.VISIBLE); mManageConferenceButton.setVisibility(View.VISIBLE); mGenericMergeButton.setVisibility(View.GONE); } @Override public void showGenericMergeButton() { mExtraRowButton.setVisibility(View.VISIBLE); mManageConferenceButton.setVisibility(View.GONE); mGenericMergeButton.setVisibility(View.VISIBLE); } @Override public void hideExtraRow() { mExtraRowButton.setVisibility(View.GONE); } }
从而，通过Ui，CallButtonUi，BaseFragment，CallButtonFragment，Presenter，CallButtonPresenter将M,V,P分开，让数据，业务，展示分开开发维护，代码变得清晰，每层只需要关注自己的东西就行，这就比我们以前都只在一个Activity或Fragment中糅杂在一起好很多。
如果有需要查看Android源码的童鞋，可以自行到Android官网下载或去下面两个网站进行在线查看。
1，http://androidxref.com
2，http://www.grepcode.com
