Use LiveData to update UI and prevent context leak

Julien LepillerWed Jun 10 23:36:19+0200 2020

284c133

Use LiveData to update UI and prevent context leak

app/src/main/java/eu/lepiller/nani/DictionaryActivity.java

44 
import android.os.AsyncTask;
55 
import android.os.Bundle;
66 
import androidx.appcompat.app.AppCompatActivity;
7+
import androidx.lifecycle.LiveData;
8+
import androidx.lifecycle.MutableLiveData;
9+
import androidx.lifecycle.Observer;
710 
import androidx.swiperefreshlayout.widget.SwipeRefreshLayout;
811 
912 
import android.util.Log;
…
2831 
2932 
public class DictionaryActivity extends AppCompatActivity {
3033 
    static final int DICO_REQUEST = 1;
31-
    static final String TAG = "DLIST";
34+
    static final String TAG = "DICO_LIST";
3235 
    DictionariesAdapter adapter;
3336 
    ArrayList<Dictionary> dictionaries;
37+
    private SwipeRefreshLayout refresher;
3438 
3539 
    @Override
3640 
    protected void onCreate(Bundle savedInstanceState) {
…
3842 
        setContentView(R.layout.activity_dictionary);
3943 
4044 
        final ListView list_view = findViewById(R.id.dictionary_view);
41-
        final SwipeRefreshLayout refresher = findViewById(R.id.dictionary_refresh_layout);
45+
        refresher = findViewById(R.id.dictionary_refresh_layout);
4246 
4347 
        dictionaries = DictionaryFactory.getDictionnaries(getApplicationContext());
4448 
        adapter = new DictionariesAdapter(this, dictionaries);
…
4751 
        if(dictionaries.size() == 0) {
4852 
            Snackbar.make(findViewById(R.id.dictionary_view), getString(R.string.no_dico_list),
4953 
                    Snackbar.LENGTH_LONG).show();
50-
            new DownloadTask(refresher).execute();
54+
            refresh();
5155 
        }
5256 
5357 
        list_view.setOnItemClickListener(new AdapterView.OnItemClickListener() {
…
5862 
                startActivityForResult(intent, DICO_REQUEST);
5963 
            }
6064 
        });
65+
    }
6166 
67+
    @Override
68+
    protected void onResume() {
69+
        super.onResume();
70+
        setObserver();
6271 
        refresher.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
6372 
            @Override
6473 
            public void onRefresh() {
65-
                new DownloadTask(refresher).execute();
74+
                refresh();
6675 
            }
6776 
        });
77+
        updateDataSet();
6878 
    }
6979 
7080 
    @Override
71-
    protected void onResume() {
72-
        super.onResume();
73-
        updateDataset();
81+
    protected void onPause() {
82+
        unsetObserver();
83+
        super.onPause();
84+
    }
85+
86+
    private void refresh() {
87+
        new DownloadTask().execute();
7488 
    }
7589 
76-
    private class DownloadTask extends AsyncTask<String, Integer, Integer> {
77-
        private SwipeRefreshLayout refresher;
90+
    private void setObserver() {
91+
        LiveData<Boolean> data = DownloadTask.getRefreshingData();
92+
        data.observe(this, new Observer<Boolean>() {
93+
            @Override
94+
            public void onChanged(Boolean refreshing) {
95+
                refresher.setRefreshing(refreshing);
96+
            }
97+
        });
98+
    }
7899 
79-
        DownloadTask(SwipeRefreshLayout r) {
80-
            refresher = r;
100+
    private void unsetObserver() {
101+
        LiveData<Boolean> data = DownloadTask.getRefreshingData();
102+
        data.removeObservers(this);
103+
    }
104+
105+
    private static class DownloadTask extends AsyncTask<String, Integer, Integer> {
106+
        final private static MutableLiveData<Boolean> refreshing = new MutableLiveData<>();
107+
108+
        static LiveData<Boolean> getRefreshingData() {
109+
            return refreshing;
81110 
        }
82111 
83112 
        @Override
84113 
        protected Integer doInBackground(String... strings) {
114+
            refreshing.postValue(true);
85115 
            try {
86116 
                URL url = DictionaryFactory.getListUrl();
87117 
                HttpURLConnection connection = (HttpURLConnection) url.openConnection();
…
119149 
        @Override
120150 
        protected void onPostExecute(Integer i) {
121151 
            super.onPostExecute(i);
122-
            refresher.setRefreshing(false);
123-
            updateDataset();
124-
            if(i == null)
125-
                return;
126-
            Snackbar.make(findViewById(R.id.dictionary_view), getString(i),
127-
                    Snackbar.LENGTH_LONG).show();
152+
            refreshing.setValue(false);
128153 
        }
129154 
    }
130155 
131-
    private void updateDataset() {
156+
    private void updateDataSet() {
132157 
        DictionaryFactory.updatePackageList();
133158 
        dictionaries.clear();
134159 
        dictionaries.addAll(DictionaryFactory.getDictionnaries(getApplicationContext()));
…
139164 
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
140165 
        super.onActivityResult(requestCode, resultCode, data);
141166 
        if (requestCode == DICO_REQUEST) {
142-
            DictionaryFactory.updatePackageList();
143-
            adapter.notifyDataSetChanged();
167+
            updateDataSet();
144168 
        }
145169 
    }
146170