Question

我的viewpager中有3页。每个页面都有一个按钮，最初设置为一个开始按钮。按下开始按钮后，它将变为暂停按钮。我的问题是，如果我在第一页并单击开始（将其更改为暂停），然后滚动到最后一页并返回到第一页，则按钮会再次开始。它已经失去了被压迫的状态。这只发生在滚动两页之后。如果仅滚动一页然后再返回，它不会丢失状态。

public Object instantiateItem(ViewGroup collection, int position) {

        RelativeLayout wholeView = new RelativeLayout(collection.getContext());

            // images
            final ImageView workoutWidget = new ImageView(collection.getContext());
            workoutWidget.setImageResource(R.drawable.workout_widget_master);

            final ImageButton resetButton = new ImageButton(collection.getContext());
            resetButton.setBackgroundDrawable(context.getResources().getDrawable(R.drawable.reset_button_master));
            RelativeLayout.LayoutParams resetButtonParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
            resetButtonParams.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
            resetButtonParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
            resetButtonParams.height = 150;
            resetButtonParams.width = 150;
            resetButton.setLayoutParams(resetButtonParams);
            resetButton.setVisibility(View.GONE);

            final ImageButton startButton = new ImageButton(collection.getContext());
            startButton.setBackgroundDrawable(context.getResources().getDrawable(R.drawable.start_button_master));
            startButton.setTag(context.getString(R.string.wtrStartButtonTag));
            RelativeLayout.LayoutParams startButtonParams = new RelativeLayout.LayoutParams(RelativeLayout.LayoutParams.WRAP_CONTENT, RelativeLayout.LayoutParams.WRAP_CONTENT);
            startButtonParams.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
            startButtonParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
            startButtonParams.height = 150;
            startButtonParams.width = 150;
            startButton.setLayoutParams(startButtonParams);
            startButton.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    startButton.setAlpha(1.0f);

                    if (startButton.getTag() == context.getString(R.string.wtrStartButtonTag)) {
                        startButton.setBackgroundDrawable(context.getResources().getDrawable(R.drawable.pause_button_master));
                        startButton.setTag(context.getString(R.string.wtrPauseButtonTag));
                        resetButton.setVisibility(View.VISIBLE);
                    }
                    else if (startButton.getTag() == context.getString(R.string.wtrPauseButtonTag)) {
                        startButton.setBackgroundDrawable(context.getResources().getDrawable(R.drawable.start_button_master));
                        startButton.setTag(context.getString(R.string.wtrStartButtonTag));
                    }
                }
            });

            // text labels view
            LinearLayout textLabels = new LinearLayout(collection.getContext());
            textLabels.setOrientation(LinearLayout.VERTICAL);

                TextView activityDescription = new TextView(collection.getContext());
                activityDescription.setText("Warm-up");
                activityDescription.setPadding(200, 200, 0, 0);
                activityDescription.setTextSize(30);
                textLabels.addView(activityDescription);

                TextView timeLeftForThisActivity = new TextView(collection.getContext());
                timeLeftForThisActivity.setText("00:00");
                timeLeftForThisActivity.setPadding(200, 0, 0, 0);
                timeLeftForThisActivity.setTextSize(60);
                textLabels.addView(timeLeftForThisActivity);

                LinearLayout elapsedLabels = new LinearLayout(collection.getContext());
                elapsedLabels.setOrientation(LinearLayout.HORIZONTAL);

                    TextView elapsedTimeStatic = new TextView(collection.getContext());
                    elapsedTimeStatic.setText("Elapsed Time: ");
                    elapsedTimeStatic.setPadding(200, 0, 0, 0);
                    elapsedTimeStatic.setTextSize(20);

                    TextView elapsedTimeDynamic = new TextView(collection.getContext());
                    elapsedTimeDynamic.setText("00:00");
                    elapsedTimeDynamic.setPadding(0, 0, 0, 0);
                    elapsedTimeDynamic.setTextSize(20);

                elapsedLabels.addView(elapsedTimeStatic);
                elapsedLabels.addView(elapsedTimeDynamic);

            textLabels.addView(elapsedLabels);

        // adding images and text to overall view
        wholeView.addView(workoutWidget);
        wholeView.addView(startButton);
        wholeView.addView(resetButton);
        wholeView.addView(textLabels);

    collection.addView(wholeView, 0);

    return wholeView;
}

Answer 1

它失去了状态，因为默认情况下viewpager只保存上一页和下一页（屏幕外页面限制为1）。如果你滚动到最后一页，那么第一页将被销毁。

您可以使用setOffscreenPageLimit(2);

增加内存中保存的页数

Answer 2

Viewpager根据当前位置工作。根据您的Android应用程序有多少个标签或片段，当前位置上一个和下一个位置。查看寻呼机仅保留下一页和上一页的内存。因此，您必须增加屏幕外页面限制的数量，以适应要刷的屏幕数量。你可以通过添加

来实现

  viewPager.setOffscreenPageLimit(2); to your code.

我希望有效。提前谢谢。

在ViewPager中滑动到新页面会导致旧页面丢失状态

2 个答案: