Intent实现页面跳转和传值

*Intent称为意图，是Android各大组件连接的桥梁

1.Activity页面跳转

同一个包内

Intent intent = new Intent();
intent.setClass(MainActivity.this, SecondActivity.class);  
MainActivity.this.startActivity(intent);

不同包内

(1)明确的Intent

Intent intent = new Intent();
ComponentName comp = new ComponentName("包名(应用本身所在的包，通过AndroidManifest.xml中package属性查看)","包名.类名(Activity所在的包)");
//或者intent.setClassName("包名","包名.类名");
intent.setComponent(comp);
startActivity(intent);

(2)不明确的Intent

Intent intent = new Intent();
intent.setAction(Intent.ACTION_MAIN); // 应用程序的入口
intent.addCategory(Intent.CATEGORY_HOME); // 桌面的应用程序
startActivity(intent);

 然后在AndroidManifest.xml中注册该过滤条件

<activity
    android:name=".OtherActivity"
    android:label="OtherActivity" >
    <intent-filter>
        <action android:name="action_name" />
        <category android:name="android.intent.category.DEFAULT" />
    </intent-filter>
</activity>

注：

*第一个Activity是外部通过不明确的Intent跳转的

*要设置第一个被启动的Activity，需要设置如下属性

<intent-filter>
    <action android:name="android.intent.action.MAIN" />
    <category android:name="android.intent.category.LAUNCHER" />
</intent-filter>

2.Activity页面跳转传值

第一种方法：(Intent)

发送方：

Intent intent = new Intent();
intent.putExtra("name", "诸葛亮");
intent.putExtra("age", 50);
intent.putExtra("IQ", 200.0f);
intent.setClass(MainActivity.this, SecondActivity.class);
MainActivity.this.startActivity(intent);

接受方：

Intent intent = getIntent();
String name = intent.getStringExtra("name");
int age = intent.getIntExtra("age", 0);
float IQ = intent.getFloatExtra("IQ", 0.0f);
textview2.setText("name:"+name+",age:"+age+",IQ:"+IQ);

第二种方法：(Bundle)

发送方：

Intent intent = new Intent();
Bundle bundle = new Bundle();
bundle.putString("name", "乔峰");
bundle.putInt("age", 40);
bundle.putFloat("weight", 70.4f);
intent.putExtras(bundle);
intent.setClass(MainActivity.this, SecondActivity.class);
startActivity(intent);

接受方:

Intent intent = getIntent();
Bundle bundle = intent.getExtras();
String name = bundle.getString("name");
int age = bundle.getInt("age");
float weight = bundle.getFloat("weight");
textview.setText(name+","+age+","+weight);

第三种方法：(Application)

首先要新建一个继承Application的MyApp类，补充属性的get/set方法

AndroidManifest.xml也要配置application的属性android:name=".MyApp"

发送方：

MyApp myApp = (MyApp) getApplication();
myApp.setName("周星驰");
Intent intent = new Intent();
intent.setClass(MainActivity.this, SecondActivity.class);
startActivity(intent);

接受方：

MyApp myApp = (MyApp) getApplication();
String name = myApp.getName();
textview = (TextView) findViewById(R.id.textview);
textview.setText(name);

第四种方法：(推荐)

对象类要实现Parclelable接口

发送方：

Intent intent = new Intent();
Person person = new Person("孙悟空",500,55.6f);
intent.putExtra("person", person);
intent.setClass(MainActivity.this, SecondActivity.class);
startActivity(intent);

接受方：

Intent intent = getIntent();
Person person = intent.getParcelableExtra("person");
textview = (TextView) findViewById(R.id.textview);
textview.setText(person.toString());

对象类：

public class Person implements Parcelable {
    private String name;
    private int age;
    private float weight;

    public Person() {
        super();
        // TODO Auto-generated constructor stub
    }

    public Person(String name, int age, float weight) {
        super();
        this.name = name;
        this.age = age;
        this.weight = weight;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public float getWeight() {
        return weight;
    }

    public void setWeight(float weight) {
        this.weight = weight;
    }

    @Override
    public String toString() {
        return "Person [name=" + name + ", age=" + age + ", weight=" + weight + "]";
    }

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

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeString(name);
        dest.writeInt(age);
        dest.writeFloat(weight);
    }

    public static final Parcelable.Creator<Person> CREATOR = new Parcelable.Creator<Person>() {
        public Person createFromParcel(Parcel in) {
            return new Person(in);
        }

        public Person[] newArray(int size) {
            return new Person[size];
        }
    };

    private Person(Parcel in) {
        name = in.readString();
        age = in.readInt();
        weight = in.readFloat();
    }
}

3.页面返回传值

被返回方：

startActivityForResult(intent, 38);

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    Bundle bundle = data.getExtras();
    String name = bundle.getString("name");
    int age = bundle.getInt("age");
    float weight = bundle.getFloat("weight");
    Toast.makeText(MainActivity.this, name+age+weight, Toast.LENGTH_LONG).show();
    super.onActivityResult(requestCode, resultCode, data);
    }

返回方：

Intent data = new Intent();
data.setClass(SecondActivity.this, MainActivity.class);
Bundle bundle = new Bundle();
bundle.putString("name", "张无忌");
bundle.putInt("age", 20);
bundle.putFloat("weight", 120.5f);
data.putExtras(bundle);
setResult(250, data);
finish();

启动Activity

上下文中，通过如下方法启动Activity
*startActivity(Intent intent)：启动新的Activity
*startActivityForResult(Intent intent, int requestCode)：指定请求码启动新的Activity

如果使用startActivityForResult()启动Activity，则必须重写onActivityResult()方法，并且该方法第一个参数与requestCode相对应

关闭Activity

上下文中，通过如下方法关闭Activity
*finish()：关闭当前Activity
*finishActivity(int requestCode)：关闭以startActivity启动的Activity
在调用finish()关闭当前Activity前，可以调用setResult(int resultCode)设置返回码。返回码在启动的Activity中通过onActivityResult()捕获

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