从另一个活动获取名称

Question

好吧，所以我创建了一个活动“区域”，其中的按钮和文本视图的网格视图，因此您可以看到按钮上的区域名称。 当你点击按钮，它会带你到“表”活动，你实际上看到+表的数量（地区名称+表的数量），但当我点击区域应用程序崩溃，因为它赢得' t在表格活动中获取该区域的名称。

我知道这很混乱，我尽我最大努力与我的解释，我把这两个适配器，一个地区和第二个表格，以最短的方式，请告诉我我做错了什么。

地区的适配器：

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; 
} 

，这是表的适配器：

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; 
} 

错误日志：

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

这是它崩溃行：

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

这是调用我的表适配器类：

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)); 
     } 
    }); 
} 

编辑

我加了这段代码到我的适配器，意图：

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); 
    } 

我得到这个错误：

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

你的应用程序崩溃，因为你想没有实例它来检索areas ArrayList中的数据。因此，没有应用程序检索数据，因此错误。

确保您areas ArrayList中具有有效数据，例如通过在其构造你的areas名单的副本供你的适配器：

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); 
}