未能將信息從一項活動傳遞給另一項活動Android工作室

Question

我想使用意圖從第一項活動向第二項活動傳遞2項信息（msgTotalCost & msgProfit），但不知道是什麼導致程序崩潰（不幸的是，應用程序已停止）。

這裏是方法的在所述第一活動代碼（按下按鈕時將被激活）：

public void sendInput(View view) { 
    Intent intent = new Intent(this, ResultActivity.class); 
    EditText editTextPurPrice = (EditText) findViewById(R.id.editText_PP); 
    EditText editTextSelPrice = (EditText) findViewById(R.id.editText_SP); 
    EditText editTextStkQty = (EditText) findViewById(R.id.editText_QTY); 
    EditText editTextLotSize = (EditText) findViewById(R.id.editText_LS); 

    Double msgPurPrice = Double.parseDouble(editTextPurPrice.getText().toString()); 
    Double msgSelPrice = Double.parseDouble(editTextSelPrice.getText().toString()); 
    int msgStkQty = Integer.parseInt(editTextStkQty.getText().toString()); 
    int msgLotSize = Integer.parseInt(editTextLotSize.getText().toString()); 

    Double totalCost = getTotalCost(msgPurPrice, msgSelPrice, msgStkQty, msgLotSize); 
    Double profit = getProfit(msgPurPrice, msgSelPrice, msgStkQty, totalCost); 

    String msgTotalCost = String.valueOf(totalCost); 
    String msgProfit = String.valueOf(profit); 
    intent.putExtra(EXTRA_TOTALCOST, msgTotalCost); 
    intent.putExtra(EXTRA_PROFIT, msgProfit); 

    startActivity(intent); 

} 

附加鍵值被放置在第一活動類下

public final static String EXTRA_TOTALCOST = "com.xxxxx.calculator.InfoActivity.totalcost"; 
public final static String EXTRA_PROFIT = "com.xxxxx.calculator.InfoActivity.profit"; 

這裏是第二活動代碼：

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    Intent intent = getIntent(); 
    String totalCost = intent.getStringExtra(InfoActivity.EXTRA_TOTALCOST); 
    String profit = intent.getStringExtra(InfoActivity.EXTRA_PROFIT); 
    TextView costOutput = (TextView) findViewById(R.id.resultTTCost); 
    TextView profitOutput = (TextView) findViewById(R.id.resultProfit); 
    costOutput.setText(totalCost); 
    profitOutput.setText(profit); 
    setContentView(R.layout.activity_result); 
} 

本地如下

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xxxxx.calculator/com.xxxxx.calculator.ResultActivity}: java.lang.NullPointerException 

Answer 1

這有什麼好做的意圖和數據傳輸。你只需要進行佈局的setContentView之前，你可以找到與findViewById視圖元素。

Answer 2

變化

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    Intent intent = getIntent(); 
    String totalCost = intent.getStringExtra(InfoActivity.EXTRA_TOTALCOST); 
    String profit = intent.getStringExtra(InfoActivity.EXTRA_PROFIT); 
    TextView costOutput = (TextView) findViewById(R.id.resultTTCost); 
    TextView profitOutput = (TextView) findViewById(R.id.resultProfit); 
    costOutput.setText(totalCost); 
    profitOutput.setText(profit); 
    setContentView(R.layout.activity_result); 
} 

到

protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_result); 
    Intent intent = getIntent(); 
    String totalCost = intent.getStringExtra(InfoActivity.EXTRA_TOTALCOST); 
    String profit = intent.getStringExtra(InfoActivity.EXTRA_PROFIT); 
    TextView costOutput = (TextView) findViewById(R.id.resultTTCost); 
    TextView profitOutput = (TextView) findViewById(R.id.resultProfit); 
    costOutput.setText(totalCost); 
    profitOutput.setText(profit); 
}