Android使用Serializable传递API数据到UniqueUnit页面崩溃如何解决

崩溃核心原因 #

1. 从DetailedCivilization跳转到UniqueUnit时，未将Civilizations序列化对象放入Intent传递，导致UniqueUnit中读取Bundle时拿到空值，调用getUnique_unit()触发空指针崩溃
2. 存在其他潜在崩溃隐患：MainActivity中JSON解析逻辑错误、API返回的unique_unit是数组类型直接用getString读取会抛类型转换异常

修复步骤 #

1. 修复DetailedCivilization的数据传递逻辑 #

首先将Civilizations对象从局部变量改为类成员变量，跳转时带入Intent：

public class DetailedCivilization extends AppCompatActivity {
    public static final String TAG = "TAG";
    // 新增类成员变量存储当前文明数据
    private Civilizations currentCivilization;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detailed_civilization);
        getSupportActionBar().setTitle("Detailed view");
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);

        Intent i = getIntent();
        Bundle data = i.getExtras();
        // 赋值给成员变量
        currentCivilization = (Civilizations) data.getSerializable("civilizationsData");

        // 原有渲染逻辑不变，把之前的v替换成currentCivilization即可
        TextView type = findViewById(R.id.civilizationType);
        type.setText(currentCivilization.getArmy_type());

        TextView title = findViewById(R.id.civilizationUniqueUnits);
        title.setText(currentCivilization.getName());

        TextView expansions = findViewById(R.id.civilizationUnitDescription);
        expansions.setText(currentCivilization.getExpansion());

        TextView bonus = findViewById(R.id.civilizationBonus);
        bonus.setText(currentCivilization.getCivilization_bonus());

        // 原有按钮逻辑不变
    }

    private void activityUnit(){
        Intent intent = new Intent(this, UniqueUnit.class);
        // 传递当前文明数据
        intent.putExtra("civilizationsData", currentCivilization);
        startActivity(intent);
    }
}

2. 修复MainActivity中的JSON解析错误 #

private void getJsonData() {
    String URL = "https://age-of-empires-2-api.herokuapp.com/api/v1/civilizations";
    RequestQueue requestQueue = Volley.newRequestQueue(this);
    JsonObjectRequest objectRequest = new JsonObjectRequest(Request.Method.GET, URL, null, new Response.Listener<JSONObject>() {
        @Override
        public void onResponse(JSONObject response) {
            try {
                JSONArray civilizations = response.getJSONArray("civilizations");
                // 修正循环条件，遍历整个文明数组
                for (int i=0; i< civilizations.length();i++){
                    JSONObject civilization = civilizations.getJSONObject(i);
                    Civilizations v = new Civilizations();

                    v.setName(civilization.getString("name"));
                    v.setArmy_type(civilization.getString("army_type"));
                    v.setExpansion(civilization.getString("expansion"));
                    v.setCivilization_bonus(civilization.getString("civilization_bonus"));
                    // 修正unique_unit解析，处理数组类型
                    JSONArray unitArray = civilization.getJSONArray("unique_unit");
                    if(unitArray.length() > 0){
                        v.setUnique_unit(unitArray.getString(0));
                    }else{
                        v.setUnique_unit("无专属单位");
                    }
                    all_civilizations.add(v);
                }
                // 循环结束后统一通知刷新，不要每次加都通知
                adapter.notifyDataSetChanged();
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.d(TAG, "onErrorResponse" + error.getMessage());
        }
    });
    requestQueue.add(objectRequest);
}

3. 给UniqueUnit增加空值防护，避免异常崩溃 #

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_unique_unit);
    getSupportActionBar().setTitle("Unique Unit");
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);

    Intent incomingIntent = getIntent();
    // 先判断是否有传递的参数
    if(incomingIntent.hasExtra("civilizationsData")){
        Civilizations v = (Civilizations) incomingIntent.getSerializableExtra("civilizationsData");
        if(v != null){
            TextView unit = findViewById(R.id.civilizationUnitDescription);
            unit.setText(v.getUnique_unit());
        }
    }
}

4. 修复Adapter中ViewHolder构造方法的编译错误 #

public ViewHolder(@NonNull View itemView) { // 修正参数写法，View和itemView之间加空格
    super(itemView);
    titleName = itemView.findViewById(R.id.civilizationUniqueUnits);
    expansionName = itemView.findViewById(R.id.civilizationUnitDescription);
    vv = itemView;
}

内容的提问来源于stack exchange，提问作者syskeyy