Android 无法在 ListView 布局中设置图像

Question

看起来好像找到了图像，但我不知道如何插入简单的适配器（或任何让我在布局中设置图像的东西） https://gyazo.com/61ab064c19ae50090f08e6436776a52e

我想为数组中的每个对象设置一个图像，例如：

monsterimglist.setImageResource(R.mipmap.icon_name);

目前我正在测试在列表视图的所有数组项中显示 R.mipmap.a1。

错误：java.lang.NullPointerException：尝试在空对象引用上调用虚方法'void android.widget.ImageView.setImageResource(int)'

有人可以帮助我吗？非常感谢

ListView monsterslistview;
ImageView monsterimg;
TextView monstername;
TextView monstertype;

private static String monsterid;
ArrayList<HashMap<String, String>> MonstersList;


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

    //Fiquem els elements creats la seva id corresponent
    monstername = (TextView) findViewById(R.id.namelayout);
    monstertype = (TextView) findViewById(R.id.typelayout);
    monsterslistview = (ListView) findViewById(R.id.monsterslistview);
    monsterimg = (ImageView) findViewById(R.id.imglayout);


    HashMap<String, String> hashMap;

    //Creem un nou objecte ArrayList per inserir les dades
    MonstersList = new ArrayList<HashMap<String, String>>();

    //..........Process JSON DATA................
        try {
            JSONObject reader = new JSONObject(loadJSONFromAsset());

            //Guardem a un Array de tipus JSON les dades
            JSONArray jr = reader.getJSONArray("monsters");
            for (int i = 0; i < jr.length(); i++) {
                JSONObject jsonObjectLine = jr.getJSONObject(i);

                // Desem els items JSON en una variable
                String id = jsonObjectLine.getString("id");
                String name = jsonObjectLine.getString("name");
                String type = jsonObjectLine.getString("type");
                String icon = jsonObjectLine.getString("icon");

                //Toast.makeText(ListMonsters.this, id, Toast.LENGTH_LONG).show();

                // Afegim la clau-valor a un objecte HashMap
                hashMap = new HashMap<String, String>();
                hashMap.put("id", id);
                hashMap.put("name", name);
                hashMap.put("type", type);
                hashMap.put("icon", icon);
                MonstersList.add(hashMap);

                //mostrem per pantalla els elements que volem mostar
                ListAdapter adapter = new SimpleAdapter(
                        ListMonsters.this,
                        MonstersList,
                        R.layout.onemonster,
                        new String[]{"name", "type","icon"},
                        new int[]{R.id.namelayout, R.id.typelayout, R.id.imglayout}

                );
                //Picasso.with(getApplicationContext()).load(R.mipmap.a1).into(monsterimglist);
                monsterslistview.setAdapter(adapter);
                //String idagafat = MonstersList.get(i).get("icon").replace(" ", "");
                monsterimg.setImageResource(R.mipmap.a1);




                monsterslistview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                        /**
                        String idagafat = MonstersList.get(position).get("id").replace(" ", "");
                        String positionagafada = String.valueOf(position);
                        openmonster(idagafat, positionagafada);
                         **/


                    }
                });

            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }


// Funció llegir json
public String loadJSONFromAsset() {
    String json = null;
    try {
        InputStream is = ListMonsters.this.getAssets().open("monsters.json");
        int size = is.available();
        byte[] buffer = new byte[size];
        is.read(buffer);
        is.close();
        json = new String(buffer, "UTF-8");
    } catch (IOException ex) {
        ex.printStackTrace();
        return null;
    }
    return json;
}

public void openmonster(String id, String pos){
    int posarray = Integer.parseInt(pos);


    Toast.makeText(ListMonsters.this, MonstersList.get(posarray).get("icon").replace(" ", ""), Toast.LENGTH_SHORT).show();
    //Toast.makeText(ListMonsters.this, MonstersList.get(posarray).get("name").replace(" ", ""), Toast.LENGTH_SHORT).show();
    //Toast.makeText(ListMonsters.this, MonstersList.get(posarray).get("type").replace(" ", ""), Toast.LENGTH_SHORT).show();
}

}

Answer 1

在创建之前关闭括号 adapter.May 因为它会改变你的结果。

更新：

    ListView monsterslistview; ImageView monsterimg; TextView monstername; TextView monstertype;

private static String monsterid; ArrayList<HashMap<String, String>> MonstersList;


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

    //Fiquem els elements creats la seva id corresponent
    monstername = (TextView) findViewById(R.id.namelayout);
    monstertype = (TextView) findViewById(R.id.typelayout);
    monsterslistview = (ListView) findViewById(R.id.monsterslistview);
    monsterimg = (ImageView) findViewById(R.id.imglayout);


    HashMap<String, String> hashMap;

    //Creem un nou objecte ArrayList per inserir les dades
    MonstersList = new ArrayList<HashMap<String, String>>();

    //..........Process JSON DATA................
        try {
            JSONObject reader = new JSONObject(loadJSONFromAsset());

            //Guardem a un Array de tipus JSON les dades
            JSONArray jr = reader.getJSONArray("monsters");
            for (int i = 0; i < jr.length(); i++) {
                JSONObject jsonObjectLine = jr.getJSONObject(i);

                // Desem els items JSON en una variable
                String id = jsonObjectLine.getString("id");
                String name = jsonObjectLine.getString("name");
                String type = jsonObjectLine.getString("type");
                String icon = jsonObjectLine.getString("icon");

                //Toast.makeText(ListMonsters.this, id, Toast.LENGTH_LONG).show();

                // Afegim la clau-valor a un objecte HashMap
                hashMap = new HashMap<String, String>();
                hashMap.put("id", id);
                hashMap.put("name", name);
                hashMap.put("type", type);
                hashMap.put("icon", icon);
                MonstersList.add(hashMap);

    }   //-----This Bracket was missed in your code


                //mostrem per pantalla els elements que volem mostar
                ListAdapter adapter = new SimpleAdapter(
                        ListMonsters.this,
                        MonstersList,
                        R.layout.onemonster,
                        new String[]{"name", "type","icon"},
                        new int[]{R.id.namelayout, R.id.typelayout, R.id.imglayout}

                );
                //Picasso.with(getApplicationContext()).load(R.mipmap.a1).into(monsterimglist);
                monsterslistview.setAdapter(adapter);
                //String idagafat = MonstersList.get(i).get("icon").replace(" ", "");
                monsterimg.setImageResource(R.mipmap.a1);




                monsterslistview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                    @Override
                    public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                        /**
                        String idagafat = MonstersList.get(position).get("id").replace(" ", "");
                        String positionagafada = String.valueOf(position);
                        openmonster(idagafat, positionagafada);
                         **/


                    }
                });

            }
        } catch (JSONException e) {
            e.printStackTrace();
        }
    }


// Funció llegir json public String loadJSONFromAsset() {
    String json = null;
    try {
        InputStream is = ListMonsters.this.getAssets().open("monsters.json");
        int size = is.available();
        byte[] buffer = new byte[size];
        is.read(buffer);
        is.close();
        json = new String(buffer, "UTF-8");
    } catch (IOException ex) {
        ex.printStackTrace();
        return null;
    }
    return json; }

public void openmonster(String id, String pos){
    int posarray = Integer.parseInt(pos);


    Toast.makeText(ListMonsters.this, MonstersList.get(posarray).get("icon").replace(" ", ""), Toast.LENGTH_SHORT).show();
    //Toast.makeText(ListMonsters.this, MonstersList.get(posarray).get("name").replace(" ", ""), Toast.LENGTH_SHORT).show();
    //Toast.makeText(ListMonsters.this, MonstersList.get(posarray).get("type").replace(" ", ""), Toast.LENGTH_SHORT).show(); }

Android 无法在 ListView 布局中设置图像

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