從另一個活動獲取名稱

Question

好吧，所以我創建了一個活動「區域」，其中的按鈕和文本視圖的網格視圖，因此您可以看到按鈕上的區域名稱。 當你點擊按鈕，它會帶你到「表」活動，你實際上看到+表的數量（地區名稱+表的數量），但當我點擊區域應用程序崩潰，因爲它贏得' t在表格活動中獲取該區域的名稱。

我知道這很混亂，我盡我最大努力與我的解釋，我把這兩個適配器，一個地區和第二個表格，以最短的方式，請告訴我我做錯了什麼。

地區的適配器：

public ArrayList<Area> areas; 

public static LayoutInflater inflater = null; 

public MyAreaAdapter(Context mContext, ArrayList<Area> areas) { 
    this.mContext = mContext; 
    this.areas = areas; 

    inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
} 

public MyAreaAdapter(Activity_Table activity_zone){ 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 

    TextView textView; 
    ImageView imageView; 

    if (convertView == null) { 
     convertView = inflater.inflate(R.layout.imagebutton_layout, null); 
    } 

     ImageView myImageView = (ImageView) convertView.findViewById(R.id.myImageView); 
     TextView areaName = (TextView) convertView.findViewById(R.id.areaName); 

    areaName.setText(areas.get(position).getName()); 

    return convertView; 
} 

，這是表的適配器：

ArrayList<Area> areas; 
ArrayList<Table> tables; 

public static LayoutInflater inflater = null; 

public MyTableAdapter(Context mContext, ArrayList<Table> tables) { 
    this.mContext = mContext; 
    this.tables = tables; 

    inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
} 

public MyTableAdapter(Activity_Table activity_table){ 
} 

@Override 
public View getView(int position, View convertView, ViewGroup parent) { 
    TextView textView; 
    ImageView imageView; 


    if (convertView == null){ 
     convertView = inflater.inflate(R.layout.imageview_table_layout, null); 
    } 

    ImageView tableImageView = (ImageView) convertView.findViewById(R.id.tableImageView); 
    TextView tableName = (TextView) convertView.findViewById(R.id.tableName); 

    tableName.setText(areas.get(position).getName() + " " + areas.get(position).getNumOFTables()); 

    return convertView; 
} 

錯誤日誌：

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object java.util.ArrayList.get(int)' on a null object reference 

這是它崩潰行：

TableName.setText(areas.get(position).getName() + " " + areas.get(position).getNumOFTables()); 

這是調用我的表適配器類：

GridView gridView; 
ArrayList<Table> tables; 
ImageView imageView; 
MyTableAdapter adapter; 


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

    Intent startIntent = getIntent(); 
    String numTables = startIntent.getStringExtra("numTables"); 

    gridView = (GridView) findViewById(R.id.gridView2); 

    OrdersDBAdapter.OrdersDBHelper ordersDBHelper = new OrdersDBAdapter.OrdersDBHelper(Activity_Table.this); 
    tables = new ArrayList<Table>(); 

    for (int i = 0; i < Integer.parseInt(numTables); i++) { 
     tables.add(new Table()); 
    }   
    adapter = new MyTableAdapter(Activity_Table.this, tables); 

    gridView.setAdapter(adapter); 

    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 

      startActivity(new Intent(getApplicationContext(), MyOrderMainActivity.class)); 
     } 
    }); 
} 

編輯

我加了這段代碼到我的適配器，意圖：

public MyTableAdapter(Context mContext, ArrayList<Table> tables, String area_name, String numTables) { 
     this.mContext = mContext; 
     this.tables = tables; 
     this.area_name = area_name; 
     this.numTables = numTables; 

     inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    } 

我得到這個錯誤：

Error:(43, 19) error: no suitable constructor found for MyTableAdapter(Activity_Table,ArrayList) constructor MyTableAdapter.MyTableAdapter(Context,ArrayList,String,String) is not applicable (actual and formal argument lists differ in length) constructor MyTableAdapter.MyTableAdapter(Activity_Table) is not applicable (actual and formal argument lists differ in length)

Answer 1

你的應用程序崩潰，因爲你想沒有實例它來檢索areas ArrayList中的數據。因此，沒有應用程序檢索數據，因此錯誤。

確保您areas ArrayList中具有有效數據，例如通過在其構造你的areas名單的副本供你的適配器：

public MyTableAdapter(Context mContext, ArrayList<Table> tables, ArrayList<Area> areas) { 
    this.mContext = mContext; 
    this.tables = tables; 
    this.areas = areas; 

    inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
}