java - 添加异步任务功能？

Question

我有一个 Activity ，我将从 API 调用中获取信息。我知道 android 的主线程，并且知道我不应该重载它。我尝试使用线程，但我认为对于应用程序的复杂性，Asynctask 将是最好的方法。

我目前正在使用 Thread().run() 但它仍然返回“跳过 x 帧，主线程中的工作太多”。我想知道如何将 Asynctask 类添加到我的应用程序以获得更好的性能。我的 Activity 使用 ExpandableListView。

首页.java:

public class Home extends Activity {

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

}

void init() {
    findViews();
    changeFont();
    clickListeners();
    assignConditions("category", "all", "1");
    categoryAllApiCall();
}

void categoryAllApiCall() {
    RestAdapter restAdapter = new RestAdapter.Builder().setEndpoint(base_url).setLogLevel(RestAdapter.LogLevel.FULL).build();
    final Category_All category_all = restAdapter.create(Category_All.class);
    category_all.getFeed(file, operation_condition, all_condition, max_depth_condition, new Callback<CategoryPojo>() {
        @Override
        public void success(CategoryPojo categoryPojo, Response response) {
            progressBar.setVisibility(View.GONE);
            final CategoryPojo category = categoryPojo;
            new Thread(new Runnable() {
                @Override
                public void run() {
                    category_id = Arrays.copyOf(category.getCategoryId(), category.getCategoryId().length);
                    category_name = Arrays.copyOf(category.getCategoryName(), category.getCategoryName().length);
                    parent_id = Arrays.copyOf(category.getParentId(), category.getParentId().length);
                }
            }).run();
            prepareListData();
            setAdapter();
        }

        @Override
        public void failure(RetrofitError error) {
            tv_title_header.setText(error.getMessage());
            progressBar.setVisibility(View.GONE);
        }
    });

}

private void prepareListData() {
    listDataHeader = new ArrayList<String>();
    listDataChild = new HashMap<String, List<String>>();
    int count = -1;
    for (int i = 0; i < category_id.length; i++) {
        List<String> child = new ArrayList<String>();
        if (parent_id[i].equals("0")) {
            count++;
            listDataHeader.add(category_name[i]);
            for (int j = 0; j < category_id.length; j++) {
                if (parent_id[j].equals(category_id[i])) {
                    child.add(category_name[j]);

                }
            }
            listDataChild.put(listDataHeader.get(count), child);
        }
    }
}

void setAdapter() {
    elv_home_body_lay.setAdapter(new HomeExpandableListAdapter(this, listDataHeader, listDataChild));
    elv_home_body_lay.setOnGroupExpandListener(new ExpandableListView.OnGroupExpandListener() {
        int previousGroup = -1;

        @Override
        public void onGroupExpand(int groupPosition) {
            if (groupPosition != previousGroup) {
                elv_home_body_lay.collapseGroup(previousGroup);
            }
            previousGroup = groupPosition;
        }
    });

    elv_home_body_lay.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
        @Override
        public boolean onChildClick(ExpandableListView parent, View v, int groupPosition, int childPosition, long id) {
            Intent intent = new Intent(Home.this, ProductListing.class);
            Bundle bundle = new Bundle();
            bundle.putString("operation_condition", "productlisting");
            bundle.putString("catids_condition", category_id[childPosition]);
            bundle.putString("catname", category_name[childPosition]);
            bundle.putString("start_row_condition", "0");
            bundle.putString("limit_condition", "10");
            intent.putExtras(bundle);
            startActivity(intent);
            return false;
        }
    });
}
}

HomeExpandableListAdapter.java

public class HomeExpandableListAdapter extends BaseExpandableListAdapter 

{

    private Context context;
    private List<String> listDataHeader;
    private HashMap<String, List<String>> listDataChild;

    public HomeExpandableListAdapter(Context context, List<String> listDataHeader, HashMap<String, List<String>> listChildData) {
        this.context = context;
        this.listDataHeader = listDataHeader;
        this.listDataChild = listChildData;
    }

    @Override
    public Object getChild(int groupPosition, int childPosititon)
    {
        return this.listDataChild.get(this.listDataHeader.get(groupPosition)).get(childPosititon);
    }

    @Override
    public long getChildId(int groupPosition, int childPosition)
    {
        return childPosition;
    }

    @Override
    public View getChildView(int groupPosition, final int childPosition, boolean isLastChild, View convertView, ViewGroup parent)
    {
        final String childText = (String) getChild(groupPosition, childPosition);

        if (convertView == null) {
            LayoutInflater infalInflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.home_child_items_lay, null);
        }

        TextView txtListChild = (TextView) convertView.findViewById(R.id.lblListItem);

        txtListChild.setTypeface(EasyFonts.robotoLight(context));

        txtListChild.setText(childText);

        return convertView;
    }

    @Override
    public int getChildrenCount(int groupPosition)
    {
        return this.listDataChild.get(this.listDataHeader.get(groupPosition)).
                size();
    }

    @Override
    public Object getGroup(int groupPosition)
    {
        return this.listDataHeader.get(groupPosition);
    }

    @Override
    public int getGroupCount()
    {
        return this.listDataHeader.size();
    }

    @Override
    public long getGroupId(int groupPosition)
    {
        return groupPosition;
    }

    @Override
    public View getGroupView(int groupPosition, boolean isExpanded, View convertView, ViewGroup parent)
    {
        String headerTitle = (String) getGroup(groupPosition);
        if (convertView == null)
        {
            LayoutInflater infalInflater = (LayoutInflater) this.context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = infalInflater.inflate(R.layout.home_group_items_lay, null);
        }

        TextView lblListHeader = (TextView) convertView.findViewById(R.id.lblListHeader);
        ImageView img=(ImageView)convertView.findViewById(R.id.imageView1);

        lblListHeader.setTypeface(EasyFonts.robotoBold(context));

        lblListHeader.setText(headerTitle);

        if(isExpanded)
        {
            img.setImageResource(R.drawable.ic_remove_grey_36pt_2x);
        }
        if(!isExpanded)
        {
            img.setImageResource(R.drawable.ic_add_grey_36pt_2x);
        }

        return convertView;
    }

    @Override
    public boolean hasStableIds()
    {
        return false;
    }

    @Override
    public boolean isChildSelectable(int groupPosition, int childPosition)
    {
        return true;
    }
}

以上代码暂时有效，但降低了应用程序性能。我如何使用 Asynctask 类在后台运行所有这些处理并仅创建可扩展 ListView 而不重载 ui 线程。

Answer 1

直接在 Thread 上调用 run() 只是同步执行代码(在同一个线程中)，就像普通的方法调用一样。您必须使用 start() 方法在后台运行。

所以改变下面的方法:

new Thread(new Runnable() {
                @Override
                public void run() {
                    category_id = Arrays.copyOf(category.getCategoryId(), category.getCategoryId().length);
                    category_name = Arrays.copyOf(category.getCategoryName(), category.getCategoryName().length);
                    parent_id = Arrays.copyOf(category.getParentId(), category.getParentId().length);
                }
            }).run();

到:

new Thread(new Runnable() {
                @Override
                public void run() {
                    category_id = Arrays.copyOf(category.getCategoryId(), category.getCategoryId().length);
                    category_name = Arrays.copyOf(category.getCategoryName(), category.getCategoryName().length);
                    parent_id = Arrays.copyOf(category.getParentId(), category.getParentId().length);
                }
            }).start();

Q: What's the difference between a thread's start() and run() methods?

A: The separate start() and run() methods in the Thread class provide two ways to create threaded programs. The start() method starts the execution of the new thread and calls the run() method. The start() method returns immediately and the new thread normally continues until the run() method returns.

The Thread class' run() method does nothing, so sub-classes should override the method with code to execute in the second thread. If a Thread is instantiated with a Runnable argument, the thread's run() method executes the run() method of the Runnable object in the new thread instead.

Depending on the nature of your threaded program, calling the Thread run() method directly can give the same output as calling via the start() method, but in the latter case the code is actually executed in a new thread.

如果你想实现AsyncTask请看This