从 Intent 中获取 Extras（变量）

Question

我想在我的 java (android) 项目 main activity 中从另一个 class 获得三个 variables。因此，我将它们放在 bundle 中，然后将其放入 Intent 中。这些变量来自我在第三个 class 中创建的 Object，如下所示：

public class Transaction {
    private float value;
    private int transaction_Date;
    private String description;

public Transaction(float value, int transaction_Date, String description){
    super();
    this.value = value;
    this.transaction_Date = transaction_Date;
    this.description = description;
}

public float getValue(){
    return value;
}
public int getTransaction_Date(){
    return transaction_Date;
}
public String getDescription(){
    return description;
}


public void setValue(float value) {
    this.value = value;
}

public void setTransaction_Date(int transaction_Date) {
    this.transaction_Date = transaction_Date;
}

public void setDescription(String description) {
    this.description = description;
}

这是我尝试将数据放入提到的 Intent:

public class AddMoneyTransaction extends AppCompatActivity implements View.OnClickListener {

Button addDepositButton;
EditText depositInput, depositInputDate, depositInputNote;

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

    //setup the Button and EditText

    addDepositButton = (Button)findViewById(R.id.addDepositButton);
    depositInput = (EditText) findViewById(R.id.depositInput);
    depositInputDate = (EditText) findViewById(R.id.depositInputDate);
    depositInputNote = (EditText) findViewById(R.id.depositInputNote);

    //get the onClickListener

    addDepositButton.setOnClickListener(this);

}

@Override
public void onClick(View view) {
    Intent depositIntent = new Intent(AddMoneyTransaction.this, AssetsOverview.class);
    Transaction deposit = new Transaction(100, 16, "random comment");
    deposit.setValue(Float.parseFloat(depositInput.getText().toString()));
    deposit.setTransaction_Date(Integer.parseInt(depositInputDate.getText().toString()));
    deposit.setDescription(depositInputNote.getText().toString());

    Bundle depositBundle = new Bundle();
    depositBundle.putFloat("value", Float.parseFloat(depositInput.getText().toString()));
    depositBundle.putInt("date", Integer.parseInt(depositInputDate.getText().toString()));
    depositBundle.putString("description", depositInputNote.getText().toString());

    depositIntent.putExtras(depositBundle);
    startActivity(depositIntent);
}

这（当然）不起作用：

//populated transaction list

protected void populateTransactionList() {

    Intent depositIntent = getIntent();
    Transaction deposit = (Transaction) getIntent().getExtras();
}

那么我怎样才能从我的 Intent 中得到我的三个变量？

Answer 1

通过intent传递自定义对象的方式是实现类似于下面给出的Transactionclass的Parcelable接口。

使交易 class 像下面给出的片段一样可打包

import android.os.Parcel;
import android.os.Parcelable;

public class `Transaction` implements Parcelable {
    private float value;
    private int transaction_Date;
    private String description;

    public Transaction(float value, int transaction_Date, String description) {
        super();
        this.value = value;
        this.transaction_Date = transaction_Date;
        this.description = description;
    }

    public float getValue() {
        return value;
    }

    public int getTransaction_Date() {
        return transaction_Date;
    }

    public String getDescription() {
        return description;
    }


    public void setValue(float value) {
        this.value = value;
    }

    public void setTransaction_Date(int transaction_Date) {
        this.transaction_Date = transaction_Date;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeFloat(this.value);
        dest.writeInt(this.transaction_Date);
        dest.writeString(this.description);
    }

    protected Transaction(Parcel in) {
        this.value = in.readFloat();
        this.transaction_Date = in.readInt();
        this.description = in.readString();
    }

    public static final Parcelable.Creator<Transaction> CREATOR = new Parcelable.Creator<Transaction>() {
        @Override
        public Transaction createFromParcel(Parcel source) {
            return new Transaction(source);
        }

        @Override
        public Transaction[] newArray(int size) {
            return new Transaction[size];
        }
    };
}

如下所示将 Parcelable 对象放入意图中

        public class AddMoneyTransaction extends AppCompatActivity implements View.OnClickListener {

        Button addDepositButton;
        EditText depositInput, depositInputDate, depositInputNote;

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

            //setup the Button and EditText

            addDepositButton = (Button)findViewById(R.id.addDepositButton);
            depositInput = (EditText) findViewById(R.id.depositInput);
            depositInputDate = (EditText) findViewById(R.id.depositInputDate);
            depositInputNote = (EditText) findViewById(R.id.depositInputNote);

            //get the onClickListener
            addDepositButton.setOnClickListener(this);

        }

        @Override
        public void onClick(View view) {
            Intent depositIntent = new Intent(AddMoneyTransaction.this, AssetsOverview.class);
           Transaction deposit = new Transaction(100, 16, "random comment");
           deposit.setValue(Float.parseFloat(depositInput.getText().toString()));
           deposit.setTransaction_Date(
Integer.parseInt(depositInputDate.getText().toString()));
           deposit.setDescription(depositInputNote.getText().toString());
           depositIntent.putExtra("data",deposit);
           startActivity(depositIntent);
        }

并接收下面给出的意图

//populated transaction list

protected void populateTransactionList() {

    Intent depositIntent = getIntent();
    Transaction deposit = depositIntent.getParcelableExtra("data");
}

Answer 2

Transaction deposit = (Transaction) getIntent().getExtras();

临时演员是Bundle。你知道这一点，因为你有：

depositIntent.putExtras(depositBundle);

填写这些额外内容。

由于您在 Bundle 上调用了 putFloat("value", ...)、putInt("date", ...) 和 putString("description", ...)，因此您将使用关联的 getter 从基于这些的 extras 中检索值键。这可以通过以下方式完成：

直接在 getIntent() 返回的 Intent 上调用 getFloatExtra()、getIntExtra() 和 getStringExtra()，或
通过getIntent().getExtras()获取extras的Bundle，然后调用getFloat()、getInt()和getString()Bundle

A Transaction 不能进入 extras，因为你不能将任意 Java 对象放入 extras。你可以做成Transactionimplement Parcelable，这样你就可以直接把它放到extras里了。

从 Intent 中获取 Extras（变量）

Get Extras (variables) out of an Intent

java

android

bundle

android-intent