Android MVP设计架构：Model层数据传递到View层

古城微笑少年丶 2023-12-31 07:14 23阅读 0赞

一个常见的场景：处于UI的View层点击了下载的Button按钮，然后转入到Presenter层，此时当然会在Presenter层里面触发Model层的下载任务代码模块。但是，View层UI控件需要实时显示下载进度怎么办？  
要知道只有Model层才真正知道下载进度，Presenter层对进度一无所知。对于这种情况有两种方法把  
需要在Presenter层的函数里面，当在调用Model层的下载请求时候实现一个回调函数（假设它叫做Callback），然后在Presenter层的匿名Callback内部类实现里面实时调用View的进度更新即可。如代码：

架构建模：

package zhangphil.demo;
    
    public interface Model<T, R> {
        R request(T t, Callback callback);
    }

package zhangphil.demo;
    
    public interface View<T> {
        void progress(T t);
    }

package zhangphil.demo;
    
    public interface Presenter<T> {
        void action(T t);
    
        void progress(int i);
    }

package zhangphil.demo;
    
    public interface Callback<T,R> {
        R call(T t);
    }

模型实现：

package zhangphil.demo;
    
    import android.os.SystemClock;
    import java.util.concurrent.CompletableFuture;
    
    public class LoadModel implements Model<String, Object> {
        private Presenter presenter;
    
        public LoadModel(Presenter presenter) {
            this.presenter = presenter;
        }
    
        @Override
        public Object request(String s, final Callback callback) {
            CompletableFuture.runAsync(new Runnable() {
                @Override
                public void run() {
                    for (int i = 0; i <= 100; i++) {
                        SystemClock.sleep(100);
    
                        if (callback != null)
                            callback.call(i);
                    }
                }
            });
    
            return null;
        }
    }

package zhangphil.demo;
    
    public interface LoadView<T> extends View<Integer> {
        void status(T t);
    }

package zhangphil.demo;
    
    public class LoadPresenter implements Presenter<String> {
        private LoadView view;
        private Model model;
    
        public LoadPresenter(LoadView view) {
            this.view = view;
            model = new LoadModel(this);
        }
    
        @Override
        public void action(String s) {
            model.request(s, new Callback<Integer, Object>() {
                @Override
                public Object call(Integer i) {
                    updateProgress(i);
                    return null;
                }
            });
        }
    
        @Override
        public void progress(int i) {
    
        }
    
        private void updateProgress(int i) {
            view.progress(i);
    
            if (i > 0 && i < 100) {
                view.status("下载中...");
            }
    
            if (i == 100) {
                view.status("下载完成");
            }
        }
    }

测试：

package zhangphil.demo;
    
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.TextView;
    
    public class MainActivity extends AppCompatActivity implements LoadView<String> {
        private TextView progress,status;
        private Button button;
    
        private Presenter presenter;
    
        private AppCompatActivity activity;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            activity = this;
    
            setContentView(R.layout.activity_main);
    
            progress = findViewById(R.id.progress);
            button = findViewById(R.id.button);
            status=findViewById(R.id.status);
    
            presenter = new LoadPresenter(this);
    
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    presenter.action("https://zhangphil.blog.csdn.net/");
                }
            });
        }
    
        @Override
        public void status(final String s) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    status.setText(s);
                }
            });
        }
    
        @Override
        public void progress(final Integer i) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    progress.setText(i + " %");
                }
            });
        }
    }

另外一种方案，不使用Callback回调，直接在Model层调用Presenter层预设的更新函数，在此函数里面进一步触发View的更新，如：

package zhangphil.demo;
    
    public interface Model<T, R> {
        R request(T t);
    }

package zhangphil.demo;
    
    public interface View<T> {
        void progress(T t);
    }

package zhangphil.demo;
    
    public interface Presenter<T> {
        void action(T t);
    
        void progress(int i);
    }

框架模型实现：

package zhangphil.demo;
    
    import android.os.SystemClock;
    import java.util.concurrent.CompletableFuture;
    
    public class LoadModel implements Model<String, Object> {
        private Presenter presenter;
    
        public LoadModel(Presenter presenter) {
            this.presenter = presenter;
        }
    
        /**
         * 模拟下载。
         *
         * @param s
         * @return
         */
        @Override
        public Object request(String s) {
            CompletableFuture.runAsync(new Runnable() {
                @Override
                public void run() {
                    for (int i = 0; i <= 100; i++) {
                        SystemClock.sleep(100);
    
                        presenter.progress(i);
                    }
                }
            });
    
            return null;
        }
    }

package zhangphil.demo;
    
    public interface LoadView<T> extends View<Integer> {
        void status(T t);
    }

package zhangphil.demo;
    
    public class LoadPresenter implements Presenter<String> {
        private LoadView view;
        private Model model;
    
        public LoadPresenter(LoadView view) {
            this.view = view;
            model = new LoadModel(this);
        }
    
        @Override
        public void action(String s) {
            model.request(s);
        }
    
        @Override
        public void progress(int i) {
            updateProgress(i);
        }
    
        private void updateProgress(int i) {
            view.progress(i);
    
            if (i > 0 && i < 100) {
                view.status("下载中...");
            }
    
            if (i == 100) {
                view.status("下载完成");
            }
        }
    }

测试：

package zhangphil.demo;
    
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.view.View;
    import android.widget.Button;
    import android.widget.TextView;
    
    public class MainActivity extends AppCompatActivity implements LoadView<String> {
        private TextView progress, status;
        private Button button;
    
        private Presenter presenter;
    
        private AppCompatActivity activity;
    
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            activity = this;
    
            setContentView(R.layout.activity_main);
    
            progress = findViewById(R.id.progress);
            button = findViewById(R.id.button);
            status = findViewById(R.id.status);
    
            presenter = new LoadPresenter(this);
    
            button.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    presenter.action("https://zhangphil.blog.csdn.net/");
                }
            });
        }
    
        @Override
        public void status(final String s) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    status.setText(s);
                }
            });
        }
    
        @Override
        public void progress(final Integer i) {
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    progress.setText(i + " %");
                }
            });
        }
    }