Question

我是Android开发的新手。我想将用户输入作为double值，然后将其传递给下一个活动，然后将其与另一个值相加，但我无法传递它。当将这个名为wins的双数组传递给活动2时，我收到一个错误。错误是：不兼容的类型。必需：找到java.util.ArrayList：double []

Activity 1
public void btnAdd_OnClick(View v)
 {
    {
        if (txtWinnings.getText().toString().isEmpty()) {
            displayToast("Please enter an amount");
        }else{
            double winning = 
  Double.parseDouble(txtWinnings.getText().toString());
            if(winning > 0) {
                winnings.add(winning);
                txtWinnings.setText("");
                txtWinnings.setHint("You have added " + (winnings.size()) + 
   " tournament winnings");
            } else {
                displayToast("You must enter an amount more than 0");
            }
        }
    }
   }

public void btnClear_OnClick(View v)
{
    if(winnings.size() < 0)
    {
        displayToast("You have no winnings to clear");
    }else {
        winnings.clear();
        displayToast("Cleared");
    }
 }

  public void btnSummary_OnClick(View v)
  {
      {
        if(winnings.size() > 0)
        {
            Intent i = new Intent(this, SummaryActivity.class);
            i.putExtra("winnings", winnings);
            startActivity(i);
        }else{
            displayToast("You must enter at least one amount of winnings");
        }
    }
  }
   public void displayToast(String message) {
    Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
  }
  }

Activity 2
public class SummaryActivity extends AppCompatActivity {
    ArrayList<Double> winnings = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_summary);
    setTitle("Summary");
    TextView lblTournaments = (TextView) findViewById(R.id.txtAverage);
    TextView lblTotal = (TextView) findViewById(R.id.txtTotal);
    TextView lblMax = (TextView) findViewById(R.id.txtMax);
    TextView lblMin = (TextView) findViewById(R.id.txtMin);
    TextView lblAverage = (TextView) findViewById(R.id.txtAverage);

    Intent i = getIntent();
    winnings = i.getDoubleArrayExtra("winnings");

}
 }

Answer 1

winnings是ArrayList<Double>。您不能像在此行那样为double[]指定它：

winnings = i.getDoubleArrayExtra("winnings");

您可以将double[]转换为List<Double>，如下所示：

List<Double> winnings = Arrays.stream(i.getDoubleArrayExtra("winnings"))
    .mapToObj(d-> d)
    .collect(Collectors.toList());

使用流有点矫枉过正，但学习流程是值得的。

编辑：

Stream可能无法使用（请参阅评论）。如果没有Stream，您可以手动清空winnings集合，然后迭代数组以再次填充它：

double[] array = i.getDoubleArrayExtra("winnings");
winnings.clear();
for(double winning : array) {
  winnings.add(winning);
}

无法将arraylist double从一个活动传递到另一个活动

1 个答案: