一、什么是MVP
在之前的開發(fā)中，采用的是android本身的MVC模式，然而隨著業(yè)務(wù)邏輯的增加，軟件的復(fù)雜度變高，MVC模式使得view層的邏輯代碼變多，代碼可讀性變差。而MVP模式將業(yè)務(wù)邏輯代碼放入presenter層。而且MVP模式使得view層和model層沒有直接交互，提高了數(shù)據(jù)安全性。
下面看看在MVP模式里通常包含的4個(gè)要素：
(1)View:負(fù)責(zé)繪制UI元素、與用戶進(jìn)行交互(在Android中體現(xiàn)為Activity，fragment);
(2)View interface:需要View實(shí)現(xiàn)的接口，View通過View interface與Presenter進(jìn)行交互，降低 耦合，方便進(jìn)行單元測試;
(3)Model:負(fù)責(zé)存儲(chǔ)、檢索、操縱數(shù)據(jù);
(4)Presenter:作為View與Model交互的中間紐帶，處理與用戶交互的負(fù)責(zé)邏輯。
UML類圖：

MVP模式UML類圖

二、以登錄為例實(shí)現(xiàn)MVP模式
view interface
<pre>
public interface LoginView {
void showLoading();

void showLoginFail(String msg);


void loginSuccess();

}
</pre>

view層繼承view interface實(shí)現(xiàn)3個(gè)方法
<pre>
public class Activity_Login extends Activity implements LoginView,View.OnClickListener{
public ILoginPresenter presenter;
public EditText et_account_login;
public EditText et_password_login;
public Button btn_login;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
et_account_login=(EditText)findViewById(R.id.Account_login);
et_password_login=(EditText)findViewById(R.id.Password_login);
btn_login=(Button)findViewById(R.id.btn_login);
btn_login.setOnClickListener(this);
presenter=new LoginPresenterImpl(this);
}

@Override
public void showLoading() {

}

@Override
public void showLoginFail(final String msg) {
   et_account_login.post(new Runnable() {
       @Override
       public void run() {
           Toast.makeText(getApplicationContext(),msg,Toast.LENGTH_SHORT).show();
           Log.e("tag","failed");
       }
   });
}

@Override
public void loginSuccess() {
    Toast.makeText(getApplicationContext(),"登錄成功",Toast.LENGTH_SHORT).show();
    Log.e("tag","success");
    SPUtils.put(getApplicationContext(),SPUtils.SP_USERNAME,et_account_login.getText().toString());
    SPUtils.put(getApplicationContext(),SPUtils.SP_PASSWORD,et_password_login.getText().toString());
}

@Override
public void onClick(View view) {
    switch (view.getId()){
        case R.id.btn_login: String username=et_account_login.getText().toString();
            String password=et_password_login.getText().toString();
            if(TextUtils.isEmpty(username)||TextUtils.isEmpty(password)){
                Toast.makeText(this,"用戶名密碼不能為空",Toast.LENGTH_SHORT).show();
            }else{
                presenter.login(username,password);
            }
            break;
    }

}

}
</pre>

model層
<pre>
public class LoginModel {
public final static int CODE_LOGIN_SUCCESS=1;
public final static int CODE_LOGIN_PASSWORD_WRONG=-2;
public final static int CODE_LOGIN_USER_WRONG=-1;
private RequestBody SetRequestBody(String username,String password){
RequestBody body=null;
okhttp3.FormBody.Builder formEncodingBuilder=new okhttp3.FormBody.Builder();
formEncodingBuilder.add(AppConstants.ParamKey.USERNAME,username);
formEncodingBuilder.add(AppConstants.ParamKey.PASSWORD,password);
body=formEncodingBuilder.build();
return body;
}
public Request LoginRequest(String username,String password){
Request request=new Request.Builder().url(AppConstants.RequestPath.LOGIN).post(SetRequestBody(username,password)).build();
return request;
}
</pre>

presenter層
<pre>
public interface ILoginPresenter {
void login(String username, String password);
}
</pre>
<pre>

public class LoginPresenterImpl implements ILoginPresenter{
private LoginView view;
private LoginModel model;
public LoginPresenterImpl(LoginView view){
this.view=view;
model=new LoginModel();
}
@Override
public void login(final String username, final String password) {
Log.e("tag","login");
view.showLoading();
Call call= App.getInstance().okHttpClient.newCall(model.LoginRequest(username,password));
call.enqueue(new Callback() {
@Override
public void onFailure(Call call, IOException e) {
Log.e("tag","connectfailed");
view.showLoginFail(e.getMessage());
}
@Override
public void onResponse(Call call, Response response) throws IOException {
Gson gson=new Gson();
LoginState state=gson.fromJson(response.body().string(),LoginState.class);

            if(state.getResult()==LoginModel.CODE_LOGIN_SUCCESS){
                Log.e("tag","loginsuccess");
                App.getInstance().user.setUsername(username);
                App.getInstance().user.setPassword(password);
                view.loginSuccess();
            }else{
                Log.e("tag","loginfailed");
                view.showLoginFail(state.getResult()+"");
            }

        }
    });
}

}
</pre>
寫文檔好難，還是先只是把代碼貼出來吧