通過 Android---MVP學(xué)習(xí)之路（一） 渤昌，我們對mvp有大體上的認(rèn)知。但是還是有問題的鹰霍。比如頁面登錄的過程中蒙兰，我退出這個activity磷瘤，然后presenter登錄回調(diào)完成后，再去響應(yīng)activity中的方法搜变。acitivity都沒了膀斋，還怎么會響應(yīng)，會造成空指針異潮匝牛。現(xiàn)在就來解決這個問題糊识。

思路：如果activity退出后绩社，我們應(yīng)該把presenter與acitvity解除關(guān)系。這樣子presenter就不會響應(yīng)activity中的方法赂苗。我們把這個稱為解綁愉耙，有解綁就會有綁定這個操作。所以拌滋，我們通過寫一個接口朴沿，來聲明這兩個操作。

因?yàn)檫@兩個操作，對于所有的presenter都會有赌渣。所以我們對共性代碼進(jìn)行抽取魏铅，之后對整個項(xiàng)目的都會慢慢抽取共性。

先看下按照下列步驟操作后的項(xiàng)目目錄結(jié)構(gòu)：

圖片.png

步驟1：先抽取View的公共方法

public interface BaseMVPViewInterface {

    public void showLoading();

    public void hideLoading();

    public void showFailError(String message);
}

修改LoginViewInterface坚芜，改成繼承 BaseMVPViewInterface

public interface LoginViewInterface extends BaseMVPViewInterface {

    public String getUserName();

    public String getUserPassword();

    public void clearName();

    public void clearPassword();

    public void go2OtherActivity();

}

步驟2：創(chuàng)建BaseMVPPresenterInterface

public interface BaseMVPPresenterInterface<V extends BaseMVPViewInterface> {

    public void attachView(V view);

    public void detachView();
}

步驟3：創(chuàng)建BaseMVPPresenterImp來實(shí)現(xiàn)BaseMVPPresenterInterface

public class BaseMVPPresenterImp<V extends BaseMVPViewInterface> implements BaseMVPPresenterInterface<V> {

    private V view;

    @Override
    public void attachView(V view) {
        this.view = view;
    }

    @Override
    public void detachView() {
        this.view = null;
    }

    public boolean isViewAttached() {
        return view != null;
    }

    public V getAttachView() {
        return view;
    }
}

步驟4：修改LoginPresenter來繼承BaseMVPPresenterImp

public class LoginPresenter extends BaseMVPPresenterImp<LoginViewInterface> {

    private Handler handler = new Handler(Looper.getMainLooper());
    private LoginBizImp loginBizImp;

    public LoginPresenter() {
        this.loginBizImp = new LoginBizImp();
    }

    public void login() {

        if (!isViewAttached()) {
            return;
        }
        getAttachView().showLoading();
        loginBizImp.login(getAttachView().getUserName(), getAttachView().getUserPassword(), new OnLoginListener() {
            @Override
            public void success() {
                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        if (!isViewAttached()) {
                            return;
                        }
                        getAttachView().hideLoading();
                        getAttachView().go2OtherActivity();
                    }
                });
            }

            @Override
            public void failure() {

                handler.post(new Runnable() {
                    @Override
                    public void run() {
                        if (!isViewAttached()) {
                            return;
                        }
                        getAttachView().showFailError("登錄失敗");
                        getAttachView().hideLoading();
                    }
                });
            }
        });
    }

    public void clear() {
        if (!isViewAttached()) {
            return;
        }
        getAttachView().clearName();
        getAttachView().clearPassword();
    }

}

步驟5：創(chuàng)建BaseMVPAcitviy來繼承你的BaseActivity并且抽取公共代碼

public class BaseMVPActivity extends HPDBaseActivity implements BaseMVPViewInterface {

    protected ProgressDialog progressDialog;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        progressDialog = new ProgressDialog(this);
    }

    @Override
    public void showLoading() {

        progressDialog.setMessage("showLoading");
        if (!progressDialog.isShowing()) {
            progressDialog.show();
        }
    }

    @Override
    public void hideLoading() {

        if (progressDialog.isShowing()) {
            progressDialog.dismiss();
        }
    }

    @Override
    public void showFailError(String message) {
        if (TextUtils.isEmpty(message)) {
            message = "發(fā)生錯誤";
        }
        Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
    }
}

步驟6：修改LoginActivity

public class LoginActivity extends BaseMVPActivity implements LoginViewInterface {

    private EditText etName, etPassword;
    private Button btnLogin, btnClear;
    private LoginPresenter loginPresenter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_login);

        initView();
        loginPresenter = new LoginPresenter();
        loginPresenter.attachView(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        loginPresenter.detachView();
    }

    private void initView() {

        etName = findViewById(R.id.et_name);
        etPassword = findViewById(R.id.et_password);
        btnLogin = findViewById(R.id.btn_login);
        btnClear = findViewById(R.id.btn_clear);

        btnLogin.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                loginPresenter.login();
            }
        });

        btnClear.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                loginPresenter.clear();
            }
        });

    }

    @Override
    public String getUserName() {
        return etName.getText().toString().trim();
    }

    @Override
    public String getUserPassword() {
        return etPassword.getText().toString().trim();
    }

    @Override
    public void clearName() {
        etName.setText("");
    }

    @Override
    public void clearPassword() {
        etPassword.setText("");
    }

    @Override
    public void go2OtherActivity() {
        Toast.makeText(this, "go2OtherActivity", Toast.LENGTH_SHORT).show();
    }

}

好了览芳，mvp的attachview和detachView很好解決了問題。現(xiàn)在還有一個問題鸿竖，如果手機(jī)屏幕旋轉(zhuǎn)等沧竟，觸發(fā)了activity的重啟，該怎么處理Presenter呢缚忧？請看 Andriod---MVP學(xué)習(xí)之路（三）