Dagger2依赖注入解析之MVP模式解耦

之前写过一篇关于Dagger2入门的一篇文章。前一篇文章只是简单的介绍了Dagger2的注解和使用，本篇文章旨在探讨Dagger2实际运用于MVP开发模式中如何解耦的问题。接下来，我们一起去看看Dagger2实际上手是如何使用的。

创建Base M、V、P层

@Inject是不能使用在抽象类的构造函数上的，所以在解耦合MVP时需要注意。

每个人对MVP开发的模式都有不同的理解，那么在我看来，黑猫白猫，只要能抓老鼠的猫就是好猫。在java编程思想中，鼓励我们使用接口来解耦合，但是又防止滥用接口。在MVP模式中，很多开发人员都是通过接口去管理View层。如果是套路式的开发，那么这样做是没有问题的，大致的业务场景熟知，能在base层进行封装，或者说调整、改动的接口不多。但是，新的行业或者产品，不确定因素太多，那么基类中可封装的接口就有一定的局限性，导致不停的修改基类来抽取接口。
我理解的MVP模式是把Activity 或者Fragment当做View层，通过泛型和Dagger结合来解耦合Presenter层和Model层。

• View层

public abstract class BaseActivity<P extends BasePresenter> extends AppCompatActivity {
    @Inject
    protected P mPresenter;
    private Activity mActivity;
    protected ProgressDialog mProgressDialog;

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) throws RuntimeException {
        super.onCreate(savedInstanceState);
        bindingDagger2(savedInstanceState);
        if (this.mPresenter == null) {
            throw new RuntimeException("没有设置Presenter或者没有重写onCreate()方法");
        } else {
            mActivity = this;
            this.mPresenter.setActivity(this);
            this.mPresenter.onCreate(savedInstanceState);
            mProgressDialog = new ProgressDialog(this);
        }
    }

    protected abstract void bindingDagger2(Bundle savedInstanceState);

    protected void showDialog(){
        mProgressDialog.setMessage("正在加载。。。");
        mProgressDialog.show();
    }
    protected void hideDialog(){
        if (mProgressDialog.isShowing()) {
            mProgressDialog.dismiss();
        }
    }
}

1.通过@Inject将Presenter注入到Activity中，申明一个Presenter的实例。
2.将当前的Activity set到Presenter中。

• Presenter层

public abstract class BasePresenter<A extends BaseActivity, M extends BaseModel> {
    protected A mActicity;
    @Inject
    protected M mModel;

    public void setActivity(A acticity) {
        this.mActicity = acticity;
    }

    @Inject
    public void setPresenter() {
        this.mModel.setPresenter(this);
    }

    public void onCreate(Bundle savedInstanceState) {

    }
    
}

1.通过@Inject将Model注入到Presenter中，申明一个Model的实例.
2.通过@Inject注入setPresenter()方法，将model与之关联。

• Model层

public abstract class BaseModel<P extends BasePresenter> {

    protected  P mPresenter;

    public void setPresenter(P presenter) {
        mPresenter = presenter;
    }
}

实现

• Activity

public class TestActivity extends BaseActivity<TestActivityPresenter> {
    @BindView(R.id.b_net)
    Button mBNet;
    @BindView(R.id.tv_home)
    TextView mTvHome;


    @Override
    protected void bindingDagger2(Bundle savedInstanceState) {
        DaggerTestActivityComponent.create().inject(this);
    }

    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) throws RuntimeException {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        ButterKnife.bind(this);
    }

    @OnClick(R.id.b_net)
    public void onViewClicked() {
        showDialog();
        //模拟网络请求
        new Thread(() -> {
            try {
                Thread.sleep(2000);
                mPresenter.doNetWorking();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start();
    }


    public void showMsg(String subject) {
        runOnUiThread(() -> {
            Toast.makeText(TestActivity.this, subject, Toast.LENGTH_SHORT).show();
            hideDialog();
        });

    }

    public void bindViewHomeData(TestData.Data data) {
        runOnUiThread(() -> {
            mTvHome.setText(data.getSubject());
            hideDialog();
        });

    }
}

• Presenter

public class TestActivityPresenter extends BasePresenter<TestActivity, TestActivityModel> {

    private static final String TAG = "TestActivityPresenter";
    @Inject
    public TestActivityPresenter() {
    }


    public void doNetWorking() {
        // 模拟网络请求返回的数据
        List<TestData> list = new ArrayList<>();

        TestData testData1 = new TestData();

        TestData.Data data1 = new TestData.Data();
        data1.setSubject("广告栏数据");
        data1.setPicUrl("http://www.baidu.com/");

        testData1.setData(data1);
        testData1.setType("banner");


        TestData testData2 = new TestData();

        TestData.Data data2 = new TestData.Data();
        data2.setSubject("主页数据");
        data2.setPicUrl("http://www.baidu.com/");

        testData2.setData(data2);
        testData2.setType("home");


        list.add(testData1);
        list.add(testData2);

        //处理数据
        mModel.parseData(list);
        
    }


    public void onBannerData(TestData.Data banner) {
        String subject = banner.getSubject();

        mActicity.showMsg(subject);
    }


    public void onHomeData(TestData.Data home) {
        String subject = home.getSubject();
        String picUrl = home.getPicUrl();
        mActicity.bindViewHomeData(home);
    }
}

• Model

public class TestActivityModel extends BaseModel<TestActivityPresenter> {


    private String banner = "banner";
    private String home = "home";


    @Inject
    public TestActivityModel() {
    }

    public void parseData(List<TestData> list) {
        // 处理完数据返回给Presenter层
        for (TestData testData : list) {
            String type = testData.getType();
            TestData.Data data = testData.getData();
            if (type.equals(banner)) {
                mPresenter.onBannerData(data);
            } else if (type.equals(home)) {
                mPresenter.onHomeData(data);
            } else {
                // 其他。。。
            }
        }
    }
}

完整代码上传至github。