Question

我有一个活动，上面有两个按钮。每个按钮打开一个新的布局。如果我将按回我的应用程序将关闭。但我想返回Mainactivity并且如果用户再次按下然后应用程序是关闭，如果他没有按下并转到第二个布局并按回然后应用程序不应该关闭。条件应该是如果用户处于Mainactivity并按下后退按钮然后应用程序关闭。如果我可以设置这个条件，我想出了关于onBackPress方法的想法

if (k==1 && Its not a Mainactivity(or the user is not inside a Mainactivity)) {//I dont know how to check for that 

    Intent i = new Intent(this,Mainactivity.class);
    startActivity(i);
    this.finish();
} else if (k==1 && Its a Mainactivity(or the user is inside a Mainactivity)) { 
  this.finish(); //then i just want to close the application,I dont know this.finish() ,It does not close the app but still it runs in background 
}

如果你们想在这里看到我的代码，这是我想要实现的一个简单例子： -

public class MainActivity extends AppCompatActivity {

    Button btn1,button2;              //Creating button;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

           super.onCreate(savedInstanceState);
           setContentView(R.layout.activity_main);
           btn1= (Button)findViewById(R.id.btn1);      //finding button1
           button2=(Button)findViewById(R.id.button2); //finding button2 
           btn1.setOnClickListener(new View.OnClickListener() {

             @Override
             public void onClick(View v) {

               setContentView(R.layout.btn1);           

            }
        });


 button2.setOnClickListener(new View.OnClickListener() {

    @Override
    public void onClick(View v) {

         setContentView(R.layout.btn2);
      }
  });

  }
}

请帮帮我。

Answer 1

在onBackPressed()中，只需检查k的值即可。如果k的值为1或2，那么再次致电setContentView(R.layout.activity_main)以显示主layout，否则请致电super.onBackPressed()以关闭MainActivity。

每次设置initializeButtons()布局后，您需要调用方法activity_main，以便从布局中获取reference按钮以及添加onClick个侦听器。

尝试：

public class MainActivity extends AppCompatActivity {

    Button button1, button2;

    int k = 0;

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

        initializeButtons();
    }

    public void initializeButtons() {
        button1 = (Button) findViewById(R.id.btn1);
        button2 = (Button) findViewById(R.id.button2); 

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                k = 1;
                setContentView(R.layout.btn1);           
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                k = 2;
                setContentView(R.layout.btn2);
            }
        });
    }

    @Override
    public void onBackPressed() {

        if (k == 1 || k == 2) {
            k = 0;
            setContentView(R.layout.activity_main);
            initializeButtons();
        } else {
            super.onBackPressed();
        }
    }
}

<强>更新
根据{{1}}部分中的讨论，如果您想在comment期间再次打开Mainctivity，请按以下方式覆盖并更新back：

onBackPressed()

希望这会有所帮助〜

Answer 2

onBackPressed()的默认行为是关闭当前Activity。在您的情况下，只有一个Activity，即MainActivity，您在其中更改布局。

当您正在更改整个内容时，您也可以在那里创建新的Activity和setContentView(R.layout.btn1)。在onClick()按钮中启动此新活动。您将获得所需的功能。

Answer 3

您的问题是您应该为每项活动制作单独的布局。当您点击btn1时，它将转到另一个活动。

但在您的代码中，您只需更改MainActivity的内容。

因此，您应该使用Intent在活动之间移动。

像这样：

Intent intent = new Intent (MainActivity.this, SecondAvtitity.class);

因此布局会发生变化，当您按back button时，应用会返回MainActivity。

当您在MainActivity并按回按钮时，该应用将会关闭。

为了更好的解释，我做了一个示例应用程序：

public class MainActivity extends AppCompatActivity {

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

    Button button1 = (Button) findViewById(R.id.button1);
    Button button2 = (Button) findViewById(R.id.button2);

    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, SecondActivity.class);
            startActivity(intent);
        }
    });

    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, ThirdActivity.class);
            startActivity(intent);
        }
    });
 }
}

Answer 4

您可以维护已添加的所有先前布局的堆栈。首先添加一个实例变量：

this.subscription = this.route.params.subscribe(
  (params: any) => {
    this.currentSelectedSite = params['id'];


    this.leaseTerminationService.fetchLeaseTerminationSite(this.currentSelectedSite)
      .subscribe(
        data => {
          const myArray = [];
          for (let key in data) {
            myArray.push(data[key]);
          }
          this.selectedLeaseTermination = myArray;
        }
      )


    //Make a call to get the SITE specific data for the selected site
    this.sitesService.getSite(this.currentSelectedSite)
      .subscribe(
        data => {
          const myArray = [];
          for (let key in data) {
            myArray.push(data[key]);

          }

          this.selectedSiteSite = myArray;
                }
      )

      //Make a call to get the LEASE specific data for the selected site
      this.leasesService.getLease(this.currentSelectedSite)
        .subscribe(
          data => {
            const myArray = [];
            for (let key in data) {
              myArray.push(data[key]);
            }

            this.selectedSiteLease = myArray;

          }
        )

        //Make a call to get the LEASE specific data for the selected site
        this.leasesService.getLeasesList(this.currentSelectedSite)
          .subscribe(
            data => {
              const myArray = [];
              for (let key in data) {
                myArray.push(data[key]);

              }

              this.selectedSiteLeases = myArray;

              // Set the count of tabs
              this.tabsCount = this.selectedSiteLeases.length;

              this.tabs = [];
              console.log('getLeasesList called');

              this.createTabs(this.selectedSiteLeases);

              // Set the first tab as the defaults after the tabs have been defined
              this.setActiveTab(0);
            }
          )

    }
  )
}

public createTabs(leases) {
    this.tabs = [];

     for (let key in leases) {
       this.tabs.push(
         {title: 'Lease ' + this.selectedSiteLeases[key].lease_id
         , content: this.selectedSiteLeases[key].renewal_latest_date }
       );
     }
   }

然后，添加以下两种方法：

Stack<Integer> layoutHistoryStack = new Stack<>();

然后，使用@Override public void onBackPressed() { if(layoutHistoryStack.size() == 1) { // the first layout that was added is shown. finish() layoutHistoryStack.pop(); finish(); return; } // pop() the current layout layoutHistoryStack.pop(); // show the prev setContentView(layoutHistoryStack.peek(), false); } public void setContentView(@LayoutRes int layoutResID, boolean addToHistoryStack) { if(addToHistoryStack) layoutHistoryStack.add(layoutResID); super.setContentView(layoutResID); }替换之前的每个setContentView(R.id.layout)来电，即添加到setContentView(R.id.layout, true)。

Answer 5

这个怎么样？它确实有效。

我已完成Ferdous's snippet：

public class MainActivity extends AppCompatActivity {

int k = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    Button button1 = (Button) findViewById(R.id.button1);
    Button button2 = (Button) findViewById(R.id.button2);

    button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            k = 1;
            setContentView(R.layout.activity_second);
        }
    });

    button2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            k = 2;
            setContentView(R.layout.activity_third);
        }
    });
}

@Override
public void onBackPressed() {

    if (k == 1 || k == 2) {
        k = 0;
        Intent intent = new Intent(this, MainActivity.class);
        startActivity(intent);
    } else {
        this.finishAffinity();
    }
}

}

在具有不同布局的背压方法上

5 个答案: