将Button设置为返回到以前的布局

Question

我是安卓工作室的新手

我正在Android Studio中构建一个关于GIRDVIEW图像的程序。我设置了2 layout：- activity_main.xml：layout1以显示Girdview图像-- layout2：solo_picture.xml只显示一个Pictuter和1个Back按钮，以帮助返回布局1当用户单击它时，.I有MainActivity.java和MyImageAdapter.java (包括代码)--这是一个问题:当我单击Back按钮时，无法返回layout1。不过，我用了：

 //want to use-save state values
Bundle myOriginalMemoryBundle;
myOriginalMemoryBundle = savedInstanceState;

.

//设置后退按钮以返回到layout1 (GridView)

btnSoloBack = (Button) findViewById(R.id.btnSoloBack);
btnSoloBack.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                // redraw the main screen showing the layout1
              onCreate(myOriginalMemoryBundle);
            }
        });

我不知道调试时为什么myOriginalMemoryBundle = NULL。之后，我的程序停止了，我不能返回layout1继续活动.帮帮你，求你..。非常感谢<3 MainActivity.java

public class MainActivity extends AppCompatActivity {

        //GUI control bound to screen1 (holding GidView)
        GridView gridview;
        //GUI controls bound to screen2 (holding single ImageView)
        TextView txtSoloMsg;
        ImageView imgSoloPhoto;
        Button btnSoloBack;
        //in case you want to use-save state values
        Bundle myOriginalMemoryBundle;

        String[] items = {"Photo-1", "Photo-2", "Photo-3", "Photo-4", "Photo-5",
                "Photo-6", "Photo-7", "Photo-8", "Photo-9", "Photo-10", "Photo-11",
                "Photo-12", "Photo-13", "Photo-14", "Photo-15",};
        Integer[] thumbnails={R.drawable.pic01_small,R.drawable.pic02_small,R.drawable.pic03_small,
                R.drawable.pic04_small,R.drawable.pic05_small,R.drawable.pic06_small,
                R.drawable.pic07_small,R.drawable.pic08_small,R.drawable.pic09_small,
                R.drawable.pic11_small,R.drawable.pic11_small,R.drawable.pic12_small,
                R.drawable.pic13_small,R.drawable.pic14_small,R.drawable.pic15_small};
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            myOriginalMemoryBundle = savedInstanceState;
            setContentView(R.layout.activity_main);
            // setup GridView with its custom adapter and listener
            gridview = (GridView) findViewById(R.id.gridview);
            gridview.setAdapter(new MyImageAdapter(this, thumbnails));
            gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                    showBigScreen(position);
                }
            });
        }//onCreate
        private void showBigScreen(int position) {
            // show the selected picture as a single frame in the second layout
            setContentView(R.layout.solo_picture);
            // plumbing – second layout
            txtSoloMsg = (TextView) findViewById(R.id.txtSoloMsg);
            imgSoloPhoto = (ImageView) findViewById(R.id.imgSoloPhoto);
            // set caption-and-large picture
            txtSoloMsg.setText(" Position= " + position + " " + items[position]);
            imgSoloPhoto.setImageResource( thumbnails[position] );
            // set GO BACK button to return to layout1 (GridView)
            btnSoloBack = (Button) findViewById(R.id.btnSoloBack);
            btnSoloBack.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    // redraw the main screen showing the GridView
                  onCreate(myOriginalMemoryBundle);
                }
            });
        }// showBigScreen
    }//Activity

MyImageAdapter.java

public class MyImageAdapter extends BaseAdapter{
    private Context context; // main activity’s context
    Integer[] smallImages; // thumbnail data set
    public MyImageAdapter(Context mainActivityContext,
                          Integer[] thumbnails) {
        context =mainActivityContext;
        smallImages = thumbnails;
    }
    // how many entries are there in the data set?
    public int getCount() {
        return smallImages.length;
    }
    // what is in a given 'position' in the data set?
    public Object getItem(int position) {
        return smallImages[position];
    }
    // what is the ID of data item in given 'position‘?
    public long getItemId(int position) {
        return position;
    }
    // create a view for each thumbnail in the data set
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        // if possible, reuse (convertView) image already held in cache
        if (convertView == null) {
            // no previous version of thumbnail held in the scrapview holder
            // define entry in res/values/dimens.xml for grid height,width in dips
            // <dimen name="gridview_size">100dp</dimen>
            // setLayoutParams will do conversion to physical pixels
            imageView = new ImageView(context);
            int gridsize = context.getResources().getDimensionPixelOffset(R.dimen.gridview_size);
            imageView.setLayoutParams(new GridView.LayoutParams(gridsize, gridsize));
            //imageView.setLayoutParams(new GridView.LayoutParams(100, 100));//NOT a good practice
            imageView.setScaleType(ImageView.ScaleType.FIT_XY);
            imageView.setPadding(5, 5, 5, 5);
        } else {
            imageView = (ImageView) convertView;
        }
        imageView.setImageResource(smallImages[position]);
        imageView.setId(position);
        return imageView;
    }//getView

}//MyImageAdapter

Answer 1

与在同一活动中定义第二个布局不同，您只需为布局"R.layout.solo_picture“定义另一个活动。

然后将选定的图像数据从activity1解析到activity2。

当您从activity2向后按回activity1时，Android将自动恢复您以前的数据。

对不起我的英语不好。英语不是我的主要语言。

使用意图解析活动之间的数据：

在activity1上：

Intent intent1 = new Intent(activity1.this, activity2.class);
intent1.putExtra("item", items[position]);
intent1.putExtra("thumbnail", thumbnails[position])
startActivity(intent1);

在activity2上：

Intent intent    = getIntent();
String item      = intent.getIntExtra("item", "");
String thumbnail = intent.getStringExtra("thumbnail", 0);

Answer 2

为布局solo_picture.xml.定义另一个活动假设您有两个活动: MainActivity和Activity2，以及两个布局: activity_main.xml和solo_picture.xml。然后，用onCreate方法编写以下代码。

MainActivity.java

setContentView(R.layout.activity_main);
Button button = (Button) findViewById((R.id.btn1));
button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(MainActivity.this, Activity2.class);
            startActivity(intent);
        }
    });

Activity2.java

setContentView(R.layout.activity2); // R.layout.solo_picture in your case
Button button = (Button) findViewById(R.id.btn2);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            Intent intent = new Intent(Activity2.this, MainActivity.class);
            startActivity(intent);
        }
    });

现在，您可以返回到第一个布局点击按钮2或按后退按钮的硬件。

确保编辑AndroidManifest.xml文件。在此文件中添加Activity2。

<activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
</activity>
<activity android:name=".Activity2"></activity>